Congrats on the new Celltei!
I think I would start off by letting him see/smell, investigate the carrier. Maybe put a few treats in there and let him go in by himself. Once he's in, keep him for a little while - maybe carry him around the house and stuff. It sounds like he may just take a little while to get used to it. Always make it a pleasant/happy place to go! I'm sure he will get accustomed to it in no time.
That's what I did with Ceiba and she was ok after a few trips in it. Good luck!!