If you want to compile firmware or utilities, we recommend first downloading EDK II from github and building a sample platform (EmulatorPkg, OVMF, ArmVirt, MdePkg, …). You can also use a UEFI Development Kit (UDK) release, which is a stable snapshot based on EDK II.
There are multiple hardware platforms using EDK II open source UEFI firmware, including MinPlatform Open Boards, MinnowBoard Max/Turbot, MinnowBoard 3, and Intel® Galileo Gen 2. This allows you to experiment and develop UEFI features on real hardware.
TianoCore uses Bugzilla to track issues and feature requests. Please review Reporting Issues and Reporting Security Issues for more information. If you would like to contribute code or fix issues, please see How To Contribute. The Tasks page has a list of projects that need attention.
Training on UEFI and EDK II : See Training