If you want to change an existing employee’s or user’s role to an administrator, you can do it from their profile. Check out the article, How to change a user’s access level / role permission to learn how to do it.
Same way, when adding a new employee, you can change their role when creating their profile. Check out the article, How to add an employee / user / computer to learn how to add a new employee/user.
On a Cloud deployment, each monitored user use a license. If you are adding the new employee so that they can supervise/monitor other employees or for administration purposes then you do not need to install the Teramind Agent on their computer. Or, if they already have an Agent installed, you can disable the monitoring of the employee so that it won't affect the license usage.