Go to your PDA by tapping on the Badger icon (it's quite tiny) on the top-left of the screen which is situated above the radar/mini-map. Scroll to "Trade Info", and enter it. Open the side menu at the bottom by tapping on it, then access the icon that looks like a globe with a trade icon at the bottom-right. This is the turf map. From here, you can set a waypoint to any gang's turf if you haven't yet discovered any dealers there - it will tell you the type of drugs each gang prefers to buy and sell. The Yardies sell Weed (marijuana/herb/ganja, whatever you call it) - so tap on their turf, which is yellow in colour, and travel there. There are a couple of dealers there which will appear as a blue dot on your mini-map as you travel past them. They won't be hard to find. Hope this helps.
