Sanctuary

This will become available after completing the main quest “When Freedom Calls”. Talk to Sturges and he will ask you to create some Beds using the workshop in Sanctuary. It doesn't matter where you place the beds so just create five beds. If you need materials, scrapping junk all around Sanctuary will allow you to gather the basic materials needed.

Next, you need to craft at least two basic wells to meet their needs. After that, you'll have to address the Food supplies. You can craft the very basic gardening option available. There are melons and gourd behind the workshop that you can harvest and use for crafting. If you need more, just wait for a few minutes for the crops to grow back. They grow quite fast so you can get busy crafting and scrapping around Sanctuary while you're at it.

Talking to Mama Murphy will ask you to build a chair for her with common materials. There are also a couple of scattered dog houses that you can store and relocate for Dogmeat to stay while you're in the settlement. Once you've met the Food requirements, you need to establish defenses around the area. The easiest way to get this done is by setting basic guard posts together. You only need one person to activate all of them. You have to get your Defense rating to at least 5.

Completing all these tasks will complete the quest.