ok, very easy, you have two lines comming out of your throttle assembly on the handle bar. one of them has an adjusting nut and a counter nut which holds it in place. adjusting nut is long, ~2-3cm (1") long, and i think it's a 10mm nut. losen the counter nut (smaller one, closer to the grip), then turn adjusting nut (it should turn easily with your fingers).
as you turn it clocwise, you insrease the free play, counterclockwise decreases it (i think). as you're turning it, have the other hand on the throttle, moving it from full closed to slightly opened, and you will fill the slack getting less (or more).
the owners manual (not repair manual) has a quick writup and a picture, it was right before the section on checking oil if my memory is correct...
if you do it with the bike running, you will see right away if you went too tight (idle will increase)
cheers!