First, go to the website and login, you will appear on the main screen like this.
Second, go to the bar on the left side of the screen and press settings.
Press the invite tab.
You can create an invite by pressing "new invite" and when the invite it pressed the user will be given the role that you assign. You can change the assigned role by pressing the arrow on the invite.
You can view all the users by selecting "users" in the settings this will show all the users that have accepted the invite. You can change the role of the person by pressing the arrow on the name and changing it shown in the second picture.
Read more about roles and making roles in roles.md