Using the M.2 NVME slot to dual boot the Khadas Edge with Captain board

Dear Mr. Gouwa:
I have the Khadas Edge with the Captain board and I can run Android from the onboard EMMC memory on the Edge. I would like to setup a dual boot system and run Ubuntu from the M.2 NVME on the bottom of the Captain board. Could you please send me instructions to install Ubuntu on the M.2 drive.
Thanks
Barry