Firstly you need to have the appropriate crafting level of materials for whatever level piece of gear you want to create. Then you need to have the Daedric Motif that allows you to craft that style, just like the other crafting styles. Finally you will need Daedric Hearts, one per piece of gear. They are the material that allows you to craft that style, just like Moonstone for Khajiit style or Molybdenum for Breton style. That's about it. Select all of these parts in the crating window and bingo, Daedric gear.

Also, keep in mind the hearts are very rare at lower levels. I did not start seeing them frequently until VR 6+ areas.