1.) Go to BIOS and disable Secure Boot (for me, I found it under "Advanced Boot Options" but yours may differ so just search).
2.) Save and exit changes and your computer will reboot.
3.) Go back to BIOS if it doesn't automatically show up after restarting
4.) Find the option to Enable CSM and then once you turn that on, you would be able to select your boot options like the Hard Drive, Disc Drive and USB if applicable.