You can access the BIOS on most motherboards by pressing the Delete [DEL] key repeatedly while the POST messages begin to scroll.
Some require a Function Key like F2 or F4 to enter the BIOS setup utility. If you watch carefully during the POST process, the system may display which key to press in order to enter the BIOS setup program. The BIOS splash screen may need to be disabled to see this.
Hint: If your keyboard is equipped with a "F Lock" key that toggles the Function Row on or off (the default on system startup is OFF), then be sure to turn on your Function Row by pressing the "F Lock" key first.