How do I add a user to a project?

You might have noticed this button before when setting up a project - and maybe you've even tried to invite somebody to join your team with it:

This is not how it's done, though. "Add user" button allows you to share an existing project with those who have already joined your team. So, in order to share a project, you need to invite a user first.

An invitation can be issued from Workspace >> Invites section: