How to prune my roses.?

Yes. It sounds like it hasn't been pruned in a while. Start at the top of the branches and cut of with clippers two feet of cane. Then work your way down until you reach either 12'' above the ground or 6'' above the new growth which ever is first. From then on keep a watch on it those branches, sound like sucker branches to me, and they are useless to the plant save for taking nutrients from the rose bush. When you see a stalk and it doesn't have any buds on it it's a sucker and you need to cut it out so the bush will have more energy to produce a second bloom later on.