I haven't seen the rifle you're talking about, but most butt pads are attached by a pair of phillips-head screws. If you look at the rear of the butt pad you should be able to find distortions in the rubber/foam where the screws were inserted, one near the top and one near the bottom. If you can find the spots where the screws were inserted, grease up the end of a phillips screwdriver so that it doesn't chew up the butt pad and insert into the distortions and you should be able to unscrew the screws and take off the butt pad. Installing the new one requires drilling holes in the new pad that line up with the holes in the stock, then sanding or grinding the sides of the new butt pad so that it doesn't stick out past the sides of the stock.
Yours may have a buttpad that is attached with some kind of adhesive instead of screws, but I'm pretty sure that you'll find screws.