Dell XPS 18 (1820, Early 2014) - Manual (Page 34)

34 │ Troubleshooting
Using advanced startup
Use advanced startup if you have problems starting up your computer
or if you want to change the computer’s startup settings, such as
allowing your computer to start up from a USB device or an optical
media.
1 Swipe from the right edge of the display to access Charms.
2 Touch Settings
→ Change PC settings→ General→ Advanced
startup → Restart now.
3 Touch the Troubleshoot option to configure various startup
settings.