If you need to get into BIOS, boot options, etc., via Windows 10:
This presumes your computer came with Win8 or later as its original operating system. UEFI was introduced with Win8. If yours started out life with an earlier version of Windows you should still be getting the good-old fashioned function key prompts when the machine is booting up just prior to when Windows itself begins to load.
1. Go to the Recovery section of the Update & Security Settings:
2. Choose the Advanced Startup option & hit the Restart now button
3. When the machine restarts you will be brought into a new Win10 startup GUI "menu"
4. Choose the Troubleshoot Option
a) Choose the Advanced sub-option
i) Choose the UEFI sub-option and hit the Restart button there
5. When the computer reboots this time you will be presented with an "old style" white-text on black screen menu that's familiar to anyone who's ever wanted to get into BIOS, startup options, etc. You know what you're trying to do from here.
Edited by britechguy, 20 October 2015 - 10:02 PM.