Download MirrorDash

Download the image

The newest image is the newest release whose name ends in -os1, -os2, ….

Then
  1. Flash it onto an SD card (8 GB or more) with Raspberry Pi Imager: Choose OS → Use custom, pick the image, then your card.
  2. Start the Pi with the card, the screen and the power plugged in. It restarts once by itself.
  3. Join MirrorDash-Setup on your phone by scanning the QR code on the screen, and pick your home Wi-Fi.

The user guide takes it from there.