To add an allowance to the app you need to start with adding the allowance widget, you can read more about widgets and how to add them here : https://help.gimi.com/en/articles/108464-the-first-step-add-widgets
After you have added the widget then you can set up the allowance by clicking on the allowance widget. You can decide when, how often and how much allowance will be paid out.
You will be able to edit the allowance whenever you want by clicking on the widget.
If you have Gimi Pro you can also add a Bonus on the Allowance.