An account can only be under a single email address, so if you want to change the email address on the account that owns the site to the one being used by the account that edits, do the following:

1. Log into the account which is an editor of the site, and change the email address on the account to something else. You can do this by going to the account page and clicking on "manage account".

2. Log out, then log into the account which owns the site.

3. Go to the Account page for that account and click on Manage Account, then update the email address to the one that you had been using for the editor account.