1) Download the appropriate ISO file.
2) Insert your USB into the computer.
3) Download Rufus here. (You will need to click on the Rufus x.x button below where it says download).
4) Open and run the Rufus USB tool.
5) Make sure your USB is selected under the Device drop-down menu.
6) Click the 'Select' button and open the correct ISO you previously downloaded. Your ISO file should be displayed in the drop-down to the left.
7) All other options should auto-fill themselves, but it is recommended that you verify all other fields are identical to the fields in the image below.
8) Click 'Start' to create the USB.
9) Select OK on the dialog box that appears.
10) Allow Rufus to run. Once finished, your USB is ready to use.