If you are trying to add these to the vanilla fabricator you may run into issues, but you would not want to touch the fabricator as they are a CORE file. You would go into the PrimalGameData BP that you made for your mod, then scroll down about 60% of the way till you see “Additional Structure Engrams”. You need to add an instance of this. It will allow you to specify “For Class”, which is where you will identify the “StorageBox_Fabricator”. Then under “Class Additions” you will need to identify the item(s) you want the fabricator to be able to craft using the “PrimalItem…”. Once again I would recommend just making a unique fabricator copy as I personally don’t know how well adding engrams to the vanilla fabricator works. Usually you have to also add the items you want to craft to the inventory list of the crafting station.