Fold the overlapping flap over the front. Glue the soft side of Velcro, one piece to each inside corner of the flap. Figure out the corresponding points on the body of the purse and glue the bristle-y side of the Velcro to two points on the body.
Add a hole on corresponding sides of the purse and set a grommet in each. Add a ball chain that is the right length for you and add a ball to the end of each side of the chain inside the purse. Add one more grommet to the front of the flap right in the middle and pull your keychain chain through. Put the keychain ring on the back side of the chain so it doesn’t pull through the hole. Voila!