HOW TO ADJUST YOUR MESH STRAP
Using a small metal tool that has a small tip on the end (small glasses screwdriver, bobby pin), put the end into the opening on the buckle like in the picture below. Slowly push down on the tool to pop the inner part of the buckle up. The buckle component should now move freely along the mesh strap.
Move the buckle to your desired position. The closer the buckle to the watch case, the tighter the strap will be on the wrist. Try to position the buckle aligned with the grooves on the back of the strap.
After positioning the buckle in your desired location, lay the strap flat on a surface. Put pressure down onto the part of the buckle that was released in Step #1 until it is back to its original position. You can apply the pressure using your figure, eraser end of a pencil, or something similar that is soft to ensure that the buckle is not scratched. This will lock the buckle back into position on the strap.
Place the watch on your wrist to make sure that is sits comfortable on your wrist. If you are not satisfied with the tightness of the strap, repeat steps 1-3.