If you want a really big butt then just do a lot of sitting on it watching tv snack on fattening stuff like, crisps, chocolate, icecream,toffee popcorn, drink plenty milky drinks and fizzy drinks, then go walking for one hour daily to biuld up muscle under fat to push up your butt, this will also help keep the rest of you resonably healthy.
Haha,...Its anything but hard..read carefully...sit on it....watch tv...eat lots of treats..?
as long as it's a round bum not a flat bum
To build muscle mass, slowly do squats, etc. with weights.