I realize many such questions have been asked and answered. BUT the answers are STILL above most peoples heads (at least mine!)
I'm new to this and when the prompt says no OS detected that is where I stop. (I don't want to screw up Windows on a brand new laptop; they make it difficult to get warranty service if you delete windows).
I am able to go to Bios and put the laptop in legacy mode and disable secure boot and UEFI whatever but still no OS is detected.
Therefore Ubuntu COULD not at this point install side by side. I am a "prompt follower" and simply can't follow anything beyond this. (Ubuntu is designed to follow prompts, that is its popular purpose - a 'for the masses OS'.) I remain stuck at the prompt where it says NO OS detected.