In Windows, uninstalling applications is generally done by either going to start > programs > (program name) > uninstall (program name) OR by going to start > control panel > add/remove programs. The control panel may be in start > settings depending on your windows version.
I recommend downloading firefox at www.mozilla.com/firefox,
going to youtube, then clicking on where the video should be, etc, and letting it walk you through the process. This type of thing should 'just work' if you let the program do its thing.