I put motor oil in my transfer case.. I did not start it an it's a 96 sportster

I'd drain it.
https://www.youtube.com/watch?v=tOoJTv9O_08

First motorcycle I've heard of with a transfer case.

Do you mean the primary Case? I would drain THAT and put the proper amount, and type of lubricant in it if that's where you put it. These are dry sump engines so you only have the Oil tank where you could put it. They do not take the same oil the rest of the engine takes.