We provide a selection of images that fits hardware best. If you need different image - use build framework and make whatever you need. Build framework relies on Debian and Ubuntu packages - you can build any combination - stable, old stable or rolling release.
Make sure you have a good & reliable SD card and a proper power supply. Archives can be flashed with Etcher (all OS) directly.
Insert the SD card into the slot, connect a cable to your network if possible or a display and power your board. (First) boot (with DHCP) takes a bit longer.