Have you tried selecting one of the Preset profiles to see if your characters bones can be automatically assigned? If one of the Presets works (the light turns green) then you can just load the corresponding t-pose.
If you need to assign the bones manually, then take a look at the tutorial video below. This explains how to create a t-pose for a custom bone rig where a t-pose file isn't available.
https://youtu.be/6ZoPf6yMf1Q
Peter
Forum Administrator
www.reallusion.com