That is if you are using a standard US keyboard. That is the key next to the (1) key at the top left side of your keyboard. That is done simply by pressing the tilde key (~). Next step is to bring up the, developers console. To get started you need to be logged into your game. Unless you have done something special to modify your game console, this will not work on XBOX or Playstation. This will only work on PC versions of, Fallout 4. The items will then appear in your inventory.
Just enter the code, and amount you want into your console. Below is a list of console codes for various pieces of power armor.