Your can add or invite users to your app so they can login to see their commissions. You 'add' a user when you enter their email address in InvoicePayout for the first time. This creates an account for the user to login with. When you do this they will receive a welcome email with instructions on how to access the application.
If the user already has an account within InvoicePayout, they you simply invite them to join your app. This allows sales people to login to InvoicePayout and view all the companies they receive commissions from. When you invite a user, they will receive an email explaining that they were added to your app and can use their same login.
There is only one administrator login for each app and any number of users that you will assign to commission rules. The number of users you can define is determined by your subscription. You can not define commission rules without having added the user to your InvoicePayout app.