In order to invite new users, follow the steps below:
Note: Only Super Amin and Project Admin can invite new users.
Go to “Administration” by selecting > Projects & Users > Invite Users
Add user email and select all or selective projects from the drop down and Invite Users.
Note: If you have reached your user license limit already? Before inviting new users, you need to upgrade the license.
Deactivated Users and Pending invites (user who did not accept invitation yet) are also counted in your license. Deleting a User or Canceling pending invite decreases the licensed user count.
Related: How do I invite bulk users?