[Baron Munchausen]

Every BIOS I have ever seen prints a message on the bootup screen telling you how to enter edit mode. Usually it's the DELETE key, but sometimes it's the ESCAPE key. You have to press the key within the few seconds that the message is showing after bootup, though.

Then you get dumped into a bunch of menus that can be navigated with arrow keys. Escape is usually the 'backup' key in this mode. Other keys like TAB and PgUp/PgDown will let you change various settings. You need to be very careful though. BIOS programs are very simple. There is little or no 'safety' checking. It is possible to set things wrong enough to completely screw up your PC.

When you've changed whatever you go to the exit menu and choose 'save and exit' and it reboots the machine with the new settings.