Workshop settlements are a new, and very welcome feature to Fallout 4, if you choose to put in the time that is. Once a workshop is unlocked, you have unfettered access to customize the hell out of that settlement. Want to scrap everything and rebuild? Or maybe focus on a single house and deck it out with your own furniture. Perhaps you want to be a good samaritan and establish some living conditions for your settlers with resources like food and water. All of these options are available to you, assuming of coure you have the material for it.
The game has exactly 30 settlements that will allow you to unlock the Workshop so you can start building and customizing. However, all of them but two will require you to complete a specific task to unlock. Sanctuary and Red Rocket Station are both available right out of the gate, and considering those two are most likely the first spots you'll come across in the game, you'll want to start brushing up on your building and crafting there.
Abernathy Farm
Complete the quest "Returning the Favor."
Boston Airport
Complete the quest "Shadows of Steel."
Bunker Hill
Complete the quest "The Battle of Bunker Hill."
The Castle
Clear the area of hostiles.
Coastal Cottage
Clear the area of hostiles.
County Crossing
Complete the offered radiant quest.
Covenant
Complete the quest "Human Error" or defeat the current residents
Croup Manor
Clear the area of hostiles.
Egret Tours Marina
Placate or defeat Phyllis Daily.
Finch Farm
Complete the quest "Out of the Fire."
Graygarden
Complete the quest "Troubled Waters."
Greentop Nursery
Complete the offered radiant quest.
Hangman's Alley
Clear the area of hostiles.
Home Plate (Diamond City House)
Purchase a housing permit from Geneva in the Mayor's office (2000 Caps).
Jamaica Plain
Clear the area of hostiles.
Kingsport Lighthouse
Clear the area of hostiles.
Murkwater Construction Site
Clear the area of hostiles.
Nordhagen Beach
Complete the offered radiant quest.
Oberland Station
Complete the offered radiant quest.
Outpost Zimonja
Clear the area of hostiles.
The Slog
Complete the offered radiant quest.
Somerville Place
Complete the offered radiant quest.
Spectacle Island
Clear the area of hostiles.
Starlight Drive-in
Clear the area of hostiles.
Sunshine Tidings Co-op
Clear the area of hostiles.
Taffington Boathouse
Clear the area of hostiles.
Tenpines Bluff
Complete the offered radiant quest.
Warwick Homestead
Complete the offered radiant quest.
