Best to do it in your room on your own as it's interactive, ie it tells you how to say something then you repeat it until you get the pronunciation correct. It's really good give it a try, as I said it's free have you seen how much this course is to buy?
Get a posting to BFG, go down the local pub of an evening - drink copious amounts of Pils and strange sticky liquors in very small glasses. Chat to barmaid, locals, the pub dog, the wall etc etc.
Continue the motion for a couple of months and then try chatting up one of the local females (not the camp bike as she speaks better English than you) if you are desperate enough for a shag then you will find your command of the lingo gets much better as time goes by.
Down side of course is that you might end up married to one of them!