Take a look at the nails...if you see the pink nervy bit,dont cut it...
Failing that,take Bunny to the vets...the nurse will trim them for you and maybe show you how to do it in future.
I cut my ferrets toenails all the time...the bunnies I get a bit nervous with as theyre not keen.Maybe get a friend to help,but like I say,dont cut the pink bits.best of luck!!x