Get a piece of leather cut so that you can tie it around your waist, or more importantly, sling it over your shoulder like they do in the WWE. Depending on your size, you'll want the front piece to be between 6 and 12 inches, tapering down to the ends and the buckle.
Buy a plate from a replica service or look for one at online sites (see Resources below). Make sure that it is at least 1/2-inch smaller all the way around than your leather.
Measure the distance between the plugs on the back of the plate. Trace a copy of the back of a plate on a piece of paper that you can lay over the back of the leather to make your punches. Punch holes that are a little smaller than the actual plug.
Push the plugs on the back of the plate through the holes and screw on the ends of the plugs to hold them in place. Some metal studs are bigger on the end you will push through the hole. Work them in sideways so as not to stretch the leather. The studs stay in place after they are straightened out.
Add studs along the sides of the belt for more bling. Get metal plates of flags or other logos that you want to decorate your belt with. Punch holes for them and insert the same way that you did the main plate.