1) Download the appropriate ISO file.
2) Insert your USB.
3) Download Rufus here. (You will need to click on the Rufus x.x button below where it says download).
4) Make sure your USB is selected under the Device drop-down menu.
5) Make sure the File System is set to FAT32.
6) Change the drop down menu to ISO Image.
7) Click the image of the CD and search for the ISO.
8) Everything else should automatically fill itself out. 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.