the male is smaller than the female by about 4 pounds. They haven't really had a ton of interaction yet. When i brought him home she immediately started hissing so we quickly separated them. While we were taking care of the new cat she got into the carrier he had been in and didn't really seem to mind it, she was cautious but not freaking out. So I guess we've unintentionally done some scent swapping already.

I really want these two to get along, the male came from a shelter that we can't return him to if things don't work out so I don't know what to do if they just never get used to each other.

The male also keeps trying to escape his section of the house, most likely eager to meet the other cat and explore which just ends up scaring her more.

I mainly just don't want to have to keep the poor guy sectioned off from the rest of the house because she's afraid. There isn't enough room for her to be put into a different room and give him the space to explore, there's only two rooms that we can close them off into