how do i change my email on this account?

Refer to the support article Change your Apple ID - Apple Support :

- If you don’t have an iPhone or iPad the support article says to, “go to https://appleid.apple.com and sign in. Then follow the onscreen instructions to change the email address associated with your Apple ID.”

- For general information, and other issues such as changes or addresses not being accepted.

- Note a recent change to the article where you can now change the email address without having to have access to your old email account.

You can't. You can only have one email address as an Apple ID. You aren't subscribing with your email address, you are subscribing with your Apple Account which has one email address associated with it.

My Apple I d is an email BUT I only use it as my Apple I d.

i have a second email on my account. When I subscribe I want to do so with secondary email.

how do I do this ?