I sell names using the External Transfer Service of Sedo.com, LLC.

If you want to buy a name, register on https://sedo.com and tell me your username.
Do not make me offers, wait when I make you an offer.

You need to agree with one of the companies that will take the name you bought from me and begin to serve it for you.
If you already use the services of companies that support domain names for you, ask them if they support .ai names.

Anguilla recommends companies from the list:

https://whois.ai/registrars.html