Please note only users with Admin/Owner privilege levels can invite new users.
From the web-app go to 'Users' and click 'Add User'. From the Create Users window, you can then start entering either an email or phone number to invite your users. You can also add multiple users at the same time if they will have the same 'Role' and 'Permission'. Once you have entered the information click 'Invite Users' and your invitations will be on their way!
For other helpful links see below: