Pick a top board and/or a bottom board of your choice. You can read about the different pieces here.
For a full tricopter frame, you need two pieces. The F3FC Tricopter top board has integrated power distribution and should only be combined with a G10 or CarbonFiber bottom board. It also comes with the necessary pinheaders. Note that the old 3D printed front spacer will not fit this board. You will need an injection moulded front spacer.