To add/invite users to Ignite, follow the three steps described in this guide.
To begin, click "Data & Configuration" in the lower left side of your screen.
Enter Settings, and then navigate to the Users & Roles section in the menu.
From here, you can invite new users via email by pressing the Invite users button in the top right.
FAQ
Q: The person I invited did not get the mail.
A: Ask the person to check their spam/junk inbox.
Q: The person I invited did not get the mail, it is not in the junkmail either.
A: Try to invite them again, there might have been a typo in the email address.