Room gather engines can be accessed once you place the item in your Room. Your room can be accessed here,by going to your profile and clicking the edit button next to "Room" on the right side of the page or by hovering over the "INV" icon at the top of the page, and then clicking "ROOMS".
Once in you will see an isometric grid containing your room items. There are two types of items that can be placed in a room, decorations and gathering engines. These can be distinguished by their unique border.
Room item border.
Gathering Engines:
These items allow you to gather additional items once placed in your room.