One way to finish it is to cut the fabric so that just a little sticks out around the edges of the hoop. Fold this over the edge to the back, to the inside of the hoop and secure it to the inside edge with glue. (I would recommend hot glue for a quick hold, although you should take care as hot glue could burn you through the fabric.)
Depending on the thickness of the fabric you are using, you may end up with more visible folds around the exterior edge of the hoop as the fabric wraps around, so you should take care to be consistent. Fold the fabric over itself the same direction each time and keep your folds equally spaced for the cleanest look. (Unless you fabric is very stretchy, it will be impossible to entirely avoid folds or creases since you are pulling fabric around a curved edge.)