I won't explain hot to modify/create new units. I already did the hard part by modeling and texturing.
For animation use Stratiotai / Knight.
You can use, modify, share, publish etc. my creation freely as long as you:
1. Take no profit from that
2. Remember that Hussars were Polish HEAVY renaissance cavalry, not light! H-E-A-V-Y. If i see you use my model as a light cavalry unit i will find you and i will kill you.