To create bootable Linux USB drives I use a free tool called LiLi. Get LiLi here and install it.

lili

Select your target USB device at the top, then choose your source.operating system. You can use LiLi to download images from a dropdown selection of distros, or you can download the .iso yourself from the vendor site and select it from your hard drive. Click the lightning bolt to start. It’s really pretty self-explanatory. Once done, eject the USB device and boot into it to test.