1. First, take the strap out of the bag and stretch it to the right length.

2. Pass one end of the belt through the ring buckle under the bag.

3. Thread the other end of the belt through the other side of the bag along the sewing line on the bag.

4. Pass this end of the belt through the ring buckle under the bag again and fix it.

5. Adjust the length of the belt to make it suitable and comfortable.