The answer to weight loss questions is always the same: burn more calories than take in. Eat healthy foods, eat often (never starve yourself) and exercise pretty much every day. But pick an exercise you like, not one somebody tells you is best. If you like bicycling, do that. If you like dancing, do that.
In spite of what you may hear, you can't really localize weight loss (or gain). You can build muscles, but "muscle in the butt and hips"? Women tend to have fat deposits in those areas. If you're trying to substitute muscle there for fat, I don't think that's going to work the same. HRT often helps people get fat there, but otherwise, I'd consider a little undie padding.
Lyric ~