1. Make sure you are on the users page.
2. Press the "+Add User" button.
3. Fill out the forms with correct information (You can edit the information after the form is submitted).
4. Select the position of your user and take a look at what your user can see depending on their position.
5. After pressing the 'Add User' button, your new User will receive an email. After confirmation your user is ready to go. Yes, it's really that easy.
By the way, you can also do this on your phone's internet browser!