You gotta use a controller and go to any settlement, then take any raw material. Then enter workshop mode, look at the materials, hold down the scrap button, then as soon as you release the scrap button, hold the store button. If you did it right, you can release the store button. Then what you have to do is accept to store and scrap the materials. Then go in the workbench, grab the materials, repeat. I recommend duping nuclear material. It yields the most caps.