Create Super Admin for existing web app

Please read carefully to save your time and my time, this is a very easy task. I already install in a "sub.domain" a php script for a restaurant waiting list. As a native function, the admin can create users with specific roles. The Super Admin we need to create with the capacity to create admins and those admins will have their own separate restaurant waiting system with all the native functions and all the native features already this script have.

This job have to be complete in 4 business days. Yes, more jobs available if this task complete satisfactory.