The first few times you use your Fusion, you may find it's a bit difficult to push the clasp through the wristband — this friction is expected with new wristbands and will ease up as you break the wristband in a little more.
Until that happens, though, try this:
Dip the end of the wristband in water, then push the clasp right through — you'll find the friction disappears! I
Check out this video demo, then try it for yourself.