Suspensions (F & R) are initialy set-up with 'sag' as a guide
Sag is the amount that the suspension compresses when the rider sits on the bike and as a guide the usual amount would be ~25% of travel.
For 100mm forks this would be 25mm.
The easiest way to measure is to place a zip tye around one of the forks stanchions (the tubes that go into the bottom of the fork, usually the shinning bits) push it down towards the seals and the CAREFULLY (with bouncing/jumping) getting on the bike, the zip tye will then be pushed up to the 'sag' level, measure and adjust preset accordingly either by winding the coil spring (as for Tora forks, I think, there should be some sort of dial/nob on top of one of the fork legs or adjusting air volume with a purpose made shock pump
Hope this helps