***This guide may contain spoilers
In order to get this achievement, you must help out three settlements throughout the wasteland. The easiest way to do this is to complete some side quests for Preston Garvey as he will tell you where to go to help different settlements. In order to receive the quests from Preston, you must save him from raiders at the Museum of Freedom. To activate the quest simply go to the museum(near Concord, South-East of Vault 111) and you will trigger a quest titled "When Freedom Calls". After finishing this quest, he will ask you to join him in Sanctuary, do so. Next, talk to him and he will give you different quests to help out different settlements, along the way you should complete the following quests for him:
"The First Step", "Returning the Favor", and "Raider Troubles at Oberland Station".
After finishing "Raider Troubles at Oberland Station" the achievement should unlock.
edit- if you don't get it after completing the listed quests, Preston Grey will continue to give you quests to help other settlements.