Secure boot Linux (HP 500-336 computer)

[Silverthunder]

HP 500-336
Motherboard: Memphis-S (Manufacturer name: Pegatron)
Motherboard Firmware: American Megatrends

I would like to
1) add the secure boot key to be able to boot to Linux Mint 19.1 Cinnamon (Similar to Ubuntu 18.04). Unless of course one is already loaded (if it's already included by HP)
2) know the steps for adding keys (for future reference)

[itsmyname]

@Silverthunder -- I think that you are on the wrong track. 

I think that the point of "secure boot" is a marker on the bootable media (DVD, CD, USB stick, or disk-drive) that certifies that the bootable image is not malicious software that should not be "trusted".

It's possible that a hacker would load some malicious software onto a USB stick, and then deliberately leave the memory-stick outside of a high-security government office, hoping that some employee will "find" the memory-stick, and insert it into a government computer, to try to "infect" every computer on that network.

[Silverthunder]

I am not sure why you think I am on the wrong track.  Perhaps I did not phrase the question well.  Here I will elaborate and rephrase.

Secure boot can be used to make sure that the computer boots to an operating system on the hard drive that has an acceptable key.  I have installed Linux Mint and now I am trying to give Linux Mint the privilege to boot while secure boot is enabled. 

[itsmyname]

@Silverthunder -- wrong track

The implementation of "secure boot" does not store any "key" anywhere on the computer. So, trying to store a key is an impossible task.

Your installation of Windows has a "key" embedded on your disk-drive. The motherboard reads the disk-drive, and searches for the key on the media (CD, DVD, USB memory-stick, disk-drive).  So, if you have MINT stored on a USB memory-stick, there must be a key stored on that memory-stick. If not, then Secure Boot will refuse to boot from the contents of the memory-stick.

So, review the source from where you obtained the "MINT-installer" software, to see if that downloadable software is compatible with Secure Boot.

Compare to taking a cheque from a somebody trying to buy something from you -- if you cannot verify the signature on the cheque, do not accept the cheque.  The buyer must go to their bank to obtain a "certified cheque" -- the bank certifies that the cheque is valid.