Power off the computer completely
Turn it on
Immediately and repeatedly press the BIOS/Setup key:
Common keys: F2, Del, F10, F12, Esc
If unsure, check the startup screen for “Press F2/Del to enter Setup”
On some systems, use a “Boot Menu” key (often F12/Esc) to select BIOS/UEFI setup
If the system boots into an OS, power off and try again, starting key presses immediately after power-on
On some laptops, disable Fast Boot/Fast Startup in Windows (optional) and retry
Once in BIOS/UEFI, use the on-screen instructions to navigate and save changes
Save and exit (or exit without saving) when finished