This repository contains prebuilt nimbus images. To download a prebuilt release go to the "release" section (https://github.com/pieye/nimbus-images/releases).
To select the latest release you can use this link: https://github.com/pieye/nimbus-images/releases/latest
Download the *.gz file from the latest release and write it to an SD card (minimum size 8GB). You can use balena etcher as an SD card writer (https://www.balena.io/etcher/)