Welcome to the Arm Development Platforms Community wiki and thank you for purchasing a Juno board.
We recommend all new users install the latest Arm Platforms software deliverables on their board, which will give you a full software stack including board firmware, system control processor (SCP) firmware, Arm Trusted Firmware, OP-TEE trusted execution environment, and either an EDK II based UEFI environment or a Linux kernel plus user-space filesystem booted via U-Boot.
Follow the instructions here to fetch and build the latest Arm Platforms deliverables, then follow the instructions here to run the deliverables on your Juno board.