Crushing the grapes is a very straight forward process that follows immediately after the destemming, and it's also done by the same amazing machine. All you want to do is burst the skin of each grape. This is necessary to release the juice from the grape. It also allows the yeast and enzymes into the grape to further break down the fibre and release even more juice along with flavour elements that will make up the character of the resulting wine.
The crushing is done immediately before the grapes are fed into either the press (for whites and rosés) or the tanks for maceration and fermentation (for reds).