How to put shaft back in ignition housing so I can put ignition barrel

I think we will need some pictures or a link to a video on your specific vehicle to get a better idea of exactly where you are in the process please. If you have the key cylinder with the key out, you need to insert the key and turn it one click clockwise to be able to insert the key cylinder with key into the assembly and push it inward with a little force to get in past the holding lock, then turn off the key to remove it like normal.