Once your brackets are setup on the bracket builder page, check the Champ box and hit Save Bracket. (checking the champ box will only work if its checked before the championship game is scored and marked final)
To manually select a champion, go to General Info under a specific division, click the drop down menu that says champ, and select a team. (This method will work even after a tournament is completed). You can also upload a photo of the champion team that will display on the public results page.
This what the final result will look like:
Public Results Home Page
Public Results Division Page w/Picture of Champion Team