Login to Real Synch and click the + Add CBX button on the dashboard:
Click the ellipsis on the far right side of your active CBX and select User Options:
Invite a User: click the dropdown in the Action column and select Grant Access.
Revoke a User's Access: click the dropdown in the Action column and select Revoke Access.
Resend an Invite: click the dropdown in the Action column and select Resend Invite.
Add a Custom Message to the invitation: this is an optional feature:
Note: Ensure you click the green Submit button at the bottom of the view prior to exiting the window.