Who: League Administrator, Match Secretary
From User Home Page go to one of:
1. Manage League > Modify League Settings (league level)
2. Competitions (competition level)
3. Divisions (division level)

This option is turned on for traveling leagues or divisions where the home league needs to assign fields. The option can be selected at the league level, competition level, or division level, depending on the circumstance. By default it is not selected or turned on at all levels. If you select it at the league level, then it will be selected for all competitions/divisions by default. Similarly, if a specific competition is set to Assign Fields by Home Team, then all divisions will be set the same.