Hello mark2311 and welcome,
One means to do this is to add another email account using the orginal admin email account. Then you can use manage emails to modify the permissions and allow the new email account to have whatever permissions you want them to have.
Hope this helps you out.
If the user that you would like to be set as the primary is already created then feel free to send me a private message with your account number and requested email to change and I would be happy to get it changed for you.