First, your GPU needs to support DX12. Also, you need to have Windows 10 installed in order to run DX12. If you do the upgrade yourself you will need to consult your motherboard/PC manufacturer for Win10 compatible drivers, especially the chipset. You will need that for all components as well (audio, GPU, etc.) If the mfr does not have Win10-specific drivers then you can try the latest Win8/Win8.1 drivers.
Good luck!