Playing with the hop up just means turning it up and down. In the pic below the blue "dial" thing is what you should see and what you should be turning up and down.
Just a note, this doesn't really increase accuracy, what it does is give the BB backspin so that it can travel in a relatively flat path until it loses enough velocity and drops. What it means is you will increase effective range with the hop up. It's all detailed somewhere in the FAQ's I'm sure.