I have a computer fixed with a IBM mother board and P III CPU. Pl let me know how to change boot device.?

Boot device is selected from within the CMOS. During boot up watch for the Manufacturers screen and select the option to enter new settings. Then select the device you wish to boot from.I have a computer fixed with a IBM mother board and P III CPU. Pl let me know how to change boot device.?when booting press DEL key, enter BIOS there change the boot device.