What model computer?
When you hit F2 and get into BIOS setup, need to find the option there that allows you set the boot order
Most of the time, resetting the BIOS defaults will make the Cd rom the first boot device, this is what you would be trying to do.
Look for boot device option and make sure that CD rom is first in the list or change to make it first device in list of boot order.
Now you can also try the reset bios defaults, usually go the last tab and there should be an option to reset defaults, try that and say yes
In either situation, you are trying to make cd the first boot device in the boot order and then hard drive 2nd boot option.
What is F11 keys supposed to do on your PC when booting?
But go through all info above and see if anything works as this is what you need