Summarize the following:
Adjust the clasp to accommodate your wrist. Sliding the clasp farther up the mesh strap (towards the watch) will tighten the strap on your wrist, and sliding the clasp down the mesh strap (away from the watch) will loosen the strap. Be careful not to drop the clasp on the floor. Due to its design, the back of the mesh watch strap will have a small groove every 18in (0.32cm) or so. The back of the clasp will have a corresponding indentation that fits snugly into any of these grooves. If you try to close the clasp without first having aligned it with a slot in the mesh strap, the clasp will be unable to close. Once you've found the best position for the watch strap and aligned it with a groove in the mesh strap, close the clasp to lock it in place. You should hear a "pop" sound as the clasp snaps shut. At this point, the watch is ready to be worn.

Summary:
Slide the clasp up or down the mesh strap. Align the back of the clasp with a groove in the mesh watch strap. Close the clasp.