Step 1: To avoid damaging the inside of the Lens, always remove the Lens from the Frame before changing the Strap.
Step 2: From the outside, press the buckle of the Strap towards the inside of the Frame to release it.
Step 3: Twist and thread the strap through the hole in the Frame. Repeat on the other side.
Step 4: Identify the left side of the Strap by the marking on the inside of the buckle. Thread this through the left side (as you wear them) of the Frame.
Step 5: Pull the Strap, you will hear a click as it clips into place. Repeat on the other side.