Basic hop up adjustment:
You need a firing lane around 40-60m long
pick a single point and make sure you can see the fall of the bb (ie do not shoot it a white wall)
adjust the hop till the bb flies straight then turns up at the end (try it you will see what I mean)
Turn the hop down a little bit and you will see that the bb now just about flies flat and then drops to the ground
If you have too much hop the bb will fly upwards, too little it will arc into the ground after a short distance.
however your hop is rubber and is affected by weather, so a cold hop will need about 100 rounds through it till it warms up a bit. It will also change/drop off a abit as the day goes on, so keep an eye on your shots, and you may find you need to adjust it a bit as the day progress's.
It can be easier with someone else stood at your shoulder watching the bb flight for you
hope that helps