To create additional admin accounts in SchoolMint, go to Settings > Add and Manage Users. Please note that only super users (aka super admins) can create new admin accounts.
You will see a box to invite users to your SchoolMint Account. You can click the "Add Invitations for a Different Role" at the bottom to send additional invitations. For each user, you'll have to specify their user type as either Super User (controls all) or Admin (controls some). If you select Admin, you will be asked to select the school(s) the admin will have access to.
(Optional) Add a message to the invite.
Send the invitation. Your admin(s) will receive an email inviting them to activate their SchoolMint account.