Make sure you have a good & reliable boot media (SD card / USB key) 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.
Different images? Missing features? -> Download SDK Looking for compatible accessories? Want to participate in development?
Specifications
* Specifications differ from hardware revision, model and software support level