Please state your OS and version of Lr.
The following help document provides step-by-step instructions on uninstalling different versions of Lightroom. Hopefully your version and operating system is listed.
If you're still having trouble uninstalling, then please let us know what system you are working on (Windows, Macintosh), and which version of Lightroom you are running.
What's stopping you from uninstalling just as you would any other program?