YARRG is designed to help pirates make profitable trades, it is not designed as a trading tutorial and some familiarity with trading in YPP is assumed. yppedia.puzzlepirates.com/Trading contains some advice on trading basics.
First look at the top of the page. You need to select your Ocean, the sort of Interface you would like and the type of Query you wish to ask.
Which ocean do you want to trade on? just click on that ocean's name.
You can choose to enter commodity and island names by typing them into a text entry field or by selecting them from a drop down menu. The "select from menu" option allows only a restricted number of options to be entered into each field.
There are currently four types of query available, which answer slightly different questions.
For pirates who know where they are going. Trades for route allows you to enter a route that you are planning to sail and find out if there are any profitable trades you can make along the way. This is for pirates who already have a definate sailing plan for some reason. Under "Enter Route" you need to type (or select from menus) the names of the islands or Archipelagoes that you plan to visit. If you wish to know about arbitrage opportunities at an island you can enter just that island name. If you enter only one Archipelago then you will get arbitrage opportunities in that archipelago, if you enter the same archipelago twice you'll get trades within that archipelago.
For pirates wanting to sell or buy a specific comodity prices for commodity returns the best buy and sell prices for the selected commodity at each island where trades are available. Type (or select from a menu) the name of one commodity at a time. This is useful for pirates wishing to purchase or sell a specific commodity and wanting the best price.
For pirates wanting more details about comodity prices at specified locations. Offers at location returns all the offers to buy and sell wood at the selected location(s). Type (or select) a commodity and the islands (or achipelagos) you are interested in. This is useful when the best buy or sell offer is for only a small quantity, you can check what the others offers are like.
For pirates just wanting to make some poe moving comodities about. Find Profitable Route finds you a profitable trading route, first select either "open-ended" (which might take you anywhere) or "circular" (which takes you back to where you started) then type (or select) your starting point (or points - you may for instance have two ships in different locations either of which you could use).
Data age tells you how long ago data was uploaded from each island in your ocean, data changes very quickly and trusting old data to be accurate is unlikely to be rewarding.
Prices for commodity and offers at location give very similar results; there will be two tables the first titled Offers to BUY your commodity, the second offers to SELL it. The tables can be resorted by your prefered heading by clicking on the arrows.
Trades for route and Find profitable route both return voyage plans. Find profitable route has an additional step to get at your results - when you enter your query you are given a list of 15 good routes for total profit and 15 good routes for profit per league which visit different islands; select your prefered route, perhaps you will choose to take the best profit or perhaps you need to miss out one island because it is blockaded or another because you don't have the charts to get to or from it. If you have asked for a trade for route or after selecting the profitable route you prefer you will get a Voyage trading plan - this provides you with instructions for what to do (buy this, sell that, sail there).
Sometimes no useful trades are available, in this case the results section says simply "No profitable trading opportunities were found".
After this there is a table reporting the age of the data used. And then a table of Relevant trades which lists just about everything you could want to know about each trade the plan suggests you make(yes, this table is fairly complicated), the ticky boxes down the side of this table allow you to choose which trades you like the look of - untick any that you are not interested in (for instance you may be uninterested in trades with a low profit margin).
These options are very useful, and not very advanced, but not needed for searching the data.
You can't trade more than fits in your hold. If you don't say anything YARRG assumes that you have infinite hold space (perhaps you will go over the route many times). You can enter a ship-type, a mass or a volume; additionally you can subtract quantities of comodities from a ship-type (for instance 'sloop - 10 grog' gives the capacity of a sloop that has 10 grog already on board); click the ? by this field to get a full description of permitted entries here.
How much poe do you have? If you don't say anything YARRG assumes you have infinite poe to spend, but you probably don't. Enter the amount you are willing to spend on commodities for trading with.
How much do you expect to lose to the dasterdly brigands? enter either a % (as eg - 1%) or a fracition (as eg - 1/100) of the goods you expect to loose to Brigands. Brigands take 10% if they defeat you, but only you know how often you are defeated. Note that this doesn't include rum-consumed, and you will need to account for that seperately.
How far are you willing to sail today? The default is 20 leagues, the maximum supported is 35. Are you willing to sail all the way accross the ocean for a profit? or would you prefer to go only a short way?
The search information is encoded in the URL - you can bookmark pages for searches you want to perform a lot and go straight to them without re-entering you data (or you can copy the URL and tell your hearties and crew mates if you want to). There's no need to come back to the introductory page each time.
Java magic - when you type things into the text entry fields YARRG will try to guess what you meant, if you pause for a moment then beneath the text entry field you'll see what YARRG thinks you meant if it's got it correct you don't have to type any more of that comodity/island name, just go on to the next one.
You'll probably want to upload data to ensure you have fresh data available, unfortunately YARRG only has a Linux upload client at present (a windows one is in the works). You should read http://yarrg.chiark.net/intro and the linked README page for information about the client which contain easy-to-follow instructions to download, install and run it in the form of a few comand line instructions that you can copy and paste.
It's all free, both free-as-in-beer or free-as-in-speach. If you're interested, read the 'development' pages for more info about how to contribute or how to run your own website using YARRG data (perhaps you don't like our colour choices)