Note: to add another account as an organizer to your event - they must register for the event first.
Go to Manage Users in the navigation bar on the left side of the screen.
Under Manage Users you will find the full list of everyone registered to your event, speakers, and attendees.
Locate the profile of your team member that you would like to add as an organizer. Click on the Edit drop-down menu, and select organizer.
That's it! Their profile will instantly change to an organizer and they will have access to all your event's tools.