To install the hand strap you must remove the two rubber feet at the back of the case and screw in the holding pegs.
Here is the Hand strap installed.
1. Remove the two rubber feet diagonally and opposed to the camera window at the back of the case.
2. Install the two metal pegs, put the washers and tighten the screws with the included tool.
3. Take the hand strap, open the flaps and slide the ends onto the metal pegs and close the flaps.