Are you trying to figure out how to get to the boot menu on a Macbook or other mac product?
Well it isn’t actually called the boot menu, but I know what you mean!
Here is how you open up the boot menu, or select the start-up options on a Macbook
If you want to boot from the CD then hold down the C key as the computer boots up
If you want to select which start-up option on your mac, then hold down the Options key as the computer boots up