Real hard to say given the lack of specific detail on the setup (probably hard to find out the exact pickup model etc and I have no experience with either you're amp or make of guitar).
However, for a very general setting for rock... try putting everything to about 3/4 then start tweaking from there - also, you the bridge pickup (the one furthest from the headstock). Distortion doesnt have to be up at full either, it took me 15 years of playing before I realised and accepted what older players were saying - rock sounds heavier and cleaner when the gain/distortion is up to a max of 2/3 on the dial.
You'll probably get better results by getting a Boss distortion or overdrive pedal - they're pretty cheap too at around $30 on E-Bay.
Hope that helps!