First, measuring time (this is a very important step, and please do it in this order): We took the exact cupboards and placed it on its exact position, WITH the iron angles already screwed in the cupboard. Then we used a pencil to mark the positions of the holes of the metal angles, on the wall.
Then we drilled in the wall for all the marks we’ve put for the iron angles, and after that we hammered in wall-plugs.