You will need the Selenium RC which you can get from:
And Java 1.5 or higher (Download Java here)
1) Install Java
2) Unpack Selenium RC.
3) Open a cmd.exe window and go to the directory containing the Selenium Server (selenium-remote-control-1.0.1\selenium-server-1.0.1)
4) Run the command below:
java -jar selenium-server.jar -htmlSuite "*firefox" "http://10.8.100.106" "C:\mytestsuite\mytestsuite.html" "C:\mytestsuite\results.html"
This should run your test suite in Firefox and write the results to the html file. Obviously you will need to change the "http://10.8.100.106" argument to your own server (this might just be localhost / 127.0.0.1)