There are 2 differant types of swivel belt clips for the protective snap on covers.  If your protective cover has a square hold in the back cover then you would use the swivel belt clip that has the circle button.  If your protective cover has 4 little holes in the back then you would choose the belt clip that has the 4 tiny screws.
These are very easy to install.  All you need is a small phillips screwdriver.

Covermycellphone carries colored belt clips to match your snap on covers.