Install WebGUI using to the instructions at:  https://github.com/plainblack/webgui/tree/WebGUI8

Create the following settings in your test site webgui.conf file:

"selenium" : {
    "server"  : "localhost",
    "port" : "4444",
    "browser" : "firefox",
    "webgui_url" : "http://whatever-your-site-is.com"
},

Make sure you select all the defaults (do not change the "admin" user password)

Pick the site design: "Style 03"  (This is the style selected for testing)

Download the Selenium server from: http://seleniumhq.org/download/)
   as of this writing it was selenium-server-standalone-2.24.1.jar
  
Running the Selenium Server (run in a separate command line/window)
   java -jar selenium-server-standalone-2.24.1.jar
   
   The -browserSessionReuse is to keep the selenium session open so you may troubleshoot page issues
   The Selenium software automatically closes the browser when the tests are concluded.  If you are writing/troubleshooting tests
   and need the browser to remain open use:
   java -jar selenium-server-standalone-2.24.1.jar -browserSessionReuse

GOTCHAS ---
   If running the selenium tests in the IDE make sure to change:
       <link rel="selenium.base" href="http://webgui.dbash.com" />  TO:  <link rel="selenium.base" href="http://whatever-your-site-is.com" />
       perl -pi -e 's/webgui.dbash.com/whatever-your-site-is.com/' *.html
       
   Selenium server not running (this may vary according to the values in your webgui.conf file):
      Error requesting http://localhost:4444/selenium-server/driver/:
      500 Can't connect to localhost:4444 (Connection refused)

Optional:

Download and install the Selenium IDE from: http://seleniumhq.org/projects/ide/

Take a look at the Selenium IDE documentation: http://seleniumhq.org/docs/02_selenium_ide.html

Youtube videos can be quite handy:
   http://www.youtube.com/watch?v=i4NTGUm6oeQ
   http://www.youtube.com/results?search_query=selenium+tutorial+for+beginner