I cannot work out how to change the Super Admin for my email account

In the CRM I have added a user called superadmin@resortpromotionsgroup.com  this is the current SUPER ADMIN.

When I first signed up..I used an account called mark@new-media-designs.com.

If I log in using the superadmin@    I do not get the control panel button.

I sign in as mark@new-media-designs.com   and get the control panel.

I then hit edit...and got the drop down box to change the  Super Admin....this box does not populate with the admin or super admin...as I have read you cannot change the new user to another Super Admin only to an admin....then have to change after....

I want to be able to access and add users from the super admin account and add new domains...

I am getting know where

Thanks