Does it have a DVD drive there? If so, most probably ( dont have pretty much experience with Asrock ) F11 should be the boot menu key there. Check for it, during startup, in the motherboard splash screen, the boot menu key and bios setup key is mentioned there.
If the conditions hold, Place the disk in the dvd drive, restart the netbook. When starting, tap and hold F11 during startup, it will enter you in the boot menu page, where all the possible boot devises are listed. Select the dvd drive using the scroll arrows, and hit enter ... the disk will start booting.