Rear rotors

I was in the middle of replacing my rear brake pads on my 93 isuzu rodeo LS 3.2L when I found that my right rear rotor had chunks out of it caused by the inside pad slipping out of place and allowing the piston to get chewed up hitting the rotor.
Now my problem. The rotor will not come off.I found a question that said "remove the axle nut" to get the rotor off.
Where is this thing.
HELP!