When you turn your Mac on, you "boot" it from the hard drive. However, when the need arises, you can boot your computer from data on other devices, such as an external hard drive or USB stick. Here is how to boot your Mac from a USB device:
1. Power your Mac on. When the white screen appears, wait for the start-up sound and press the "Option" key found near the space bar.
2. Once you do that, you will be presented with a list of different drives. On the right side, you will be able to see your USB drive (usually orange in color). Using your mouse or arrow keys, click the USB icon to start booting from it. You will be able to see the DVD or CD disc which you can also use to boot your Mac.
3. From there, follow the prompt or on-screen instructions.
1. Power your Mac on. When the white screen appears, wait for the start-up sound and press the "Option" key found near the space bar.
2. Once you do that, you will be presented with a list of different drives. On the right side, you will be able to see your USB drive (usually orange in color). Using your mouse or arrow keys, click the USB icon to start booting from it. You will be able to see the DVD or CD disc which you can also use to boot your Mac.
3. From there, follow the prompt or on-screen instructions.