Push belt through slot with teeth facing inward.
Wrap around the end.
Eyeball amount of tail to pull back through the terminator.
Place tail into opening.
Put a small screw driver through hole to use as a handle - it can take a bit of force to pull the tail through.
Pull the tail through. May need to push a bit to get teeth to engage.

If belt doesn't want to grab the tail, use a razor knife to clean slot opening where tail is being insrted - try to chamfer it a bit more and smooth it out.