How do I grant admin rights to another Zoho Creator user?

How do I grant admin rights to another Zoho Creator user?

How can I grant admin rights to another user of our zoho creator? There are two of us who use are currently using it, I am able to edit any of our applications while the other can not. The application is shared with the other user, and they can access it and enter data but they are unable to edit the app. We are currently using the free version of Zoho Creator. Do we need to upgrade, or is there a step I have missed?

Thanks!