Don't know how to boot from CD/DVD and/or USB

Every time your PC turns on, for a slight second it shows you what keys you could press to do something else rather then just turn in on. 

Since you're trying to boot from a drive (USB or CD) you want to enter a boot order settings. Every PC opens a boot order settings with a different key, but it's ussualy ESC, F12 or F2 keys. Pay close attention to the information your PC provides to you when you turn it on. If it will help, reboot it few times, it really won't hurt the computer. Once you've successfully opened the boot settings, with keyboard arrows navigate to the drive you're trying to boot from (eg USB DRIVE) and press Enter. 

Here's a list of Force Boot keys for a lot of computers.

Booting from USB/CD on Mac is very easy. Just hold down the Option key when the Mac turns on. You'll see a list of devices you can boot from.

To boot on your Mac, reboot it and press the "C" key repeatedly. The boot settings will open.

To enter BIOS pay attention to the information your computer gives you every time you turn it on. Ussualy it's the Delete button. So when you turn on your PC, press the Delete button repeatedly until you enter the BIOS. In there, you'll have to navigate your way to boot order settings. It's not the same process for every computer but here's an overview:

Follow these steps:

1. Select Advanced BIOS features.
2. Select Boot device order.
3. Make a desired device a Primary Boot Device.
4. Save the changes and exit the BIOS settings by pressing the key listed somewhere on the screen.