In order to obtain this Trophy, you must complete the quest The Grand Tour.
After meeting the gang bosses you must now begin taking over the other areas of Nuka World. You must exterminate every threat and erect a flag for a gang at the following locations:
Magical Kingdom
World of Refreshment
Safari Zone
Dry Rock Gulch
Galactic Zone
Once done you must speak to Gage to complete the quest, unlocking the trophy.