1. Navigate to Communities > Special Events > Friends Asking Friends > Kintera Thon.
  2. Hover over your event and select Website Info. 
  3. Click Website Features.
  4. Mark the Participation Registration checkbox.
  5. Click Save.
  6. Navigate back to Website Info and click the green Publish This Event Now button
To disable registration, follow the steps above but at step 3, unmark the box instead.