How can I change my apple id?

See this Apple article: Change your Apple ID

Change your Apple ID - Apple Support (SG)

Then see this Apple article: What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support

I'm afraid your post is very confusing.

I don't know what you mean by using one email address (which is what your Apple ID is) for your primary email. What primary email? Do you mean your iCloud email address? You can't use an entire email address as part of another address. I can't be John@xyz.com@iCloud.com

If what you mean is you want to change your primary iCloud Mail username ____@icloud.com to something else such a bacd@iCloud.com, you cannot. Once you have chosen one it is permanent. You can, however, use aliases.

Add and manage email aliases for iCloud Mail on iCloud.com - Apple Support - "An email alias is an email address that conceals your actual email address from a recipient. An alias can help you manage the email you receive, and monitor the sources of unwanted messages. You can both send and receive email from an email alias using Mail on iCloud.com.

"Note: You can’t delete or turn off a primary iCloud Mail address. You can’t use an alias to create a separate Apple ID, and an email alias can’t be converted to a primary iCloud Mail address."

That article explains how to change your the email address that is associated with your apple id. I want to start using my apple id email address as my primary email and what to change the name of the email. Is that possible?

Sorry for the confusion but you understood correctly. I wanted to change the username. Thank you for clarifying that it cannot be done.