A team captain cannot be moved to an existing team when their status is that of "captain".  The captain must fist be demoted to a team member and then moved.  

Step One: Promote an existing member to Team Captain
  1. Navigate to Communities > Special Events > Friends Asking Friends > Kintera Thon.
  2. Hover over the event and select Bookkeeping.
  3. Click Manage Initiative Records.
  4. Search for the existing participant/team member that needs to be promoted to team captain.
  5. Click Edit.
  6. Under Edit Registration Information, click "Become a Team Captain of an Existing Team."
  7. In the pop up box, select the appropriate team.
  8. Click Close.

Step Two: Move the previous Team Captain
  1. Navigate to Communities > Special Events > Friends Asking Friends > Kintera Thon.
  2. Hover over the event and select Event Admin.
  3. Click Manage Teams and Team Members.
  4. Select the current team of the previous captain who is being moved. 
  5. Highlight the last name of the previous captain.
  6. Click Move Participant.
  7. In the pop up box, select the appropriate team.
  8. Click Close. 

The previous team captain has now been replaced and moved to the new team.