Unfortunately, if you have already registered a domain name, you cannot “swap it” for another. The process of changing your domain name to another is as follows:

1. Cancel the old/incorrect domain name. (If you no longer require it)
2. Register the new domain name. (At full registration price)
3. Once the new domain is registered and set up on the server, you will need to upload the content from the old site to the new site.