Can't share form to other users

Can't share form to other users

I am trying to add users to a Private Form on Creator. I have looked through the help description on how to do this, but the "Add user" button as shown on the help pages does not show on my application. I have tried adding users at the home page, but these users do not show on the share list either. I am on a free version.

I have attached a screenshot of what I see.

Am I missing something totally obvious!?