Event coordinators can be staff members, which are constituents with an active constituency of Staff, or constituent groups of a type that can coordinate events.

To make an individual constituent a coordinator,
  1. Go to constituent record
  2. Go to Personal info tab > Constituencies tab.  Click Add > Staff.
To make a constituent group a coordinator, 
  1. Go to committee or group record
  2. Click Edit committee or edit group under Tasks.
  3. Mark off the option Can Coordinate Events.
  4. Click Save.