After registering a domain name, you get it in your own possession for a certain period of time. These rights can be sold or transferred to others.
All you need to do is follow the same steps that the buyer did when purchasing their own first domain name, as well as sending the new name to their website.
After all, the duration of the use of your domain name increases its importance. Changing the domain name leads to the loss of the previously worked hard on the old name. Have to register a new domain with a new name.