Disclaimer: Boring Video.
I tested.. you don't have to watch the video.
If you would like to select boot sequence:
Press F12 key on bootup.
If you own a Dell E7470 Dell Laptop and would like to go into bios,..
Press F2 key on bootup.
You don't have to watch this video.. the title and description should be enough to help you.
Have a good one. This would probably hold true for a Dell Latitude E7270
