In Fallout 4 there is a new feature where you can build up settlements. You should get this over the natural progression of the game, however if you would like to grind it out all you need to do is make a simple item 100x. Wooden Crates are one of the easier ones to make.
To craft you have to have the workshop unlocked for a settlement. Once you've done this, press the back button which will take you into building mode.