UX Feeback - On Adding Objects to List of Objects through backend

I have an object with a property thats a list of users.
When I go to add additional users to that list through the UI, its hard to tell that I need to enter an email to do that - I thought the “add” button was the entry point for that flow.

Might make sense to add feedback when the add button is clicked, indicating the type of and the fact that an input is required in the text field beside it.