Set the multimedia projector up to display the input the PC is connected to. If you didn't use a splitter, the PC's image will appear on your primary monitor and not your multimedia projector, and ...

Connect the 3.5 mm plug on the audio cable to your computer's Line Out or Headphone jack, and insert the other end into your projector's Audio input.

This post discusses wirelessly projecting and screen mirroring your Windows computer or laptop to an external display like a TV or a Projector using Miracast technology.

As the name suggests, the MSI Projector PC actually has a fully working PC inside the projector, and instead of needing a monitor you just use the projected image to view the PCs display.