Connect the other end of the video cable you connected to your PC's second video output port to an available input on your multimedia projector that corresponds with the type of video cable you're ...

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.

The Apple USB-C VGA Multiport Adapter lets you mirror your Mac display to a VGA-enabled projector, TV or display in up to 1080p HD. Thankfully there are cheaper third-party USB-C to VGA adapters.