What your going to do:
1) navigate to users -> manage users (https://my.ringplan.com/users)
2) Click "Add User" and invite a user to the system.
3) the user will get an invite in their email which they must click on to accept. This will help to ensure that the email you entered is working correctly and they will get other emails and notifications later on.
4) If they don't see the invite, make sure that it didn't go to their spam folder. This would be a good opportunity to whitelist emails from RingPlan. Whitelist ringplan.com emails if you have not already.