At the back of the cabinet I wanted two plugs, one for power and one for ethernet. I connected a PC style power plug to a electrical outlet extender trough a electrical box. I 3D printed the holders for the outlet.
After that I inserted the PC and monitor. If you're interested in the specs of the PC:
3rd gen Intel core i7
16GB DDR3 RAM
GTX 780 Graphics card
650W power supply
I also added the audio amp and speakers
After that I was finally able to play some games!