If you want to use a fixed average for a tournament. Perhaps your players' league averages to run a tournament.
Under your tournament event, go to Menu > Manage > Players/Teams > Players.
Select the division they will be playing in for their bracket.
Under the column called : Custom Value (1, 2 or 3)
Insert the average you want your players to use. (You can write directly in the grid, arrow down to the next, save once in a while.)
(This will not changed throughout the bracket. This will be fixed)
Then,
Under Menu > Manage > Brackets/Round-Robins > Brackets.
Choose the bracket you want to set.
Pencil to edit.
Go to Score Input section.
Under Handicap,
Insert the Custom Value column where you marked all of their averages.
Make sure to also tell the system the calculate method for the handicap.