@seongkok
It depends on how your computer's
BIOS are set up. It's an extreme rarity that a computer is not set by default to first check if there is a bootable medium in the disc drive. If such a disc is present in the drive, it will boot from it.
If your computer is not so configured, the procedure is normally to just hit the F11, Esc, or some other function key located atop your keyboard while your machine boots. Doing that will bring up a selection dialog, from which you can use the arrow keys on your keyboard to choose to boot your computer from the disc drive. Doing that will boot the UberStudent Live System. From it, you can test and install the system.
It is essential that your burned the UberStudent ISO file
as an image and not
as data for it to boot.
The Beginner's Guide should have all the info you need to get going. Unless you already have experience getting going with Linux systems, I recommend you read it from start to finish before installing UberStudent. It's advisable to print all of the info and have it aside you when installing UberStudent. Installation is not actually difficult, but there are enough everyday unfamiliarities with the details of the process to make it inadvisable to simply go by memory after reading the Guide.
Just post here again if you need additional assistance.