the Super Admin account is the Username and Pasword combination that you create during the install of power store. the Supper Admin account is created by default.
you can create other Admin accounts while logged in as the super admin by going to User -> Add User and setting the user group to Administrator.
to back up your power store, Save a copy of all the power store files for your site, and back up the database using phpMyAdmin to export the data base to a sql file.