Unetbootin goes on your hard drive. When you download the LXLE ISO, it also goes on your hard drive. Then you fire up Unetbootin, and you tell it "I want you to burn this ISO to this USB drive". You will then have a Linux LiveUSB stick. After that, reboot your computer, and during startup, it should boot you into the Live version of the OS, which will have an option to install LXLE to your hard drive, wiping out Winblows in the process. Or you can ask a local computer nerd to do it for you :)