Your best bet would be to find a host or cohost with a ton of properties near you. Reach out to them and tell them you want to learn how to host Airbnbs. Ask them if they could use an assistant and try to learn from there. Otherwise you need a property with an airbnb.
for what it’s worth, Co Host sounds like a position with less responsibility since it insinuates you are helping another host, but that’s not the case. You are a the main host to a property. There are some instances where you can help a host with some basic stuff, but I don’t that would help you learn the ropes. The only kind of co hosting I know is full service host.