Upon powering on the laptop, press F10
Select the option to modify the BIOS settings
Go to the Boot Options screen
Set Secure Boot to Disabled
Set BIOS mode to UEFI and Legacy or CSM and UEFI OS
Save settings and reboot
When the Samsung screen comes up again, press F10
With certain Samsung notebooks (like the 300E) holding F3 during boot will bring up the Boot from Disc option.