Anybody know how to transfer photos /pics from either Camera Roll or My Photo Stream onto albums?

Used to be so easy to do on iOS.6 but since the 7 download it's been a complete puzzle how to do this.....

Forgot to add - this is on my iPad 3

Open, for example, Photo Stream, tap 'Select' top right, choose the photos you want, tap 'Add to' on the top left, select an existing album, or create a new one.