Firstly you will need to login to your administrator dashboard.
Once you have logged in you will need to click on the link 'Add users, reset passwords, and more'.
Next check the tick box next to the user 'Admin Account' and click on the 'Edit Selected Users' icon. It looks like a pencil.
You can now select any of the valid email addresses you currently have configured on the account. Please be aware that once you select the new address you will then need to use this address to login to your admin account going forward.