I'm not certain this applies to your board, but my ASRock Intel board has this option in the Exit screen:
Launch EFI Shell from filesystem device
Copy shellx64.efi to the root directory to launch EFI Shell.
What is meant to happen is this option will cause the board to search for the "shellx64.efi" file in a bootable device connected to the PC.
I've read that can be a USB flash drive with the shellx64.efi file copied to its root directory. You provide your own copy of the shellx64.efi file.
Searching the Internet will provide several free sources. Personally, I've had poor luck running it, it never works right. Also, I've read the file name must be other than "shellx64.efi", you may find that in your search hits too.
I know another AMD user was able to do what you are trying to do, they had a thread that is a few pages back from this one if you care to find it.