There will be a indepth guide from the motherboard manufacturer, with details of what you type in.
But in general it is, create a bootable floppy disk, execute the bios to the disk. Restart the pc, going into the BIOS setting the floppy drive as first boot, put the floppy disk in and save and exit. The pc will boot from the disk, and will go to dos, here you will have to type something in/follow instructions from the manual that you should pront off. The pc will restart, go into BIOS and then turn the PC off. Clear CMOS and start the PC up and put the settings to what they were (may be a good idea to set the date in the BIOS.)