Here is a guide made by the person who created the script
http://ilfirin.org/graal/gadgets/gstatus.rbx . And make sure that in your profile you have "Show online status" checked, or the script won't work.
Or, as Kaimetsu said, just look in a profile and change relevant sections.
As a side note for people who are wondering how this works, and I thought this was pretty ingenious:
the cgi script downloads the public viewprofile.php for that user and scans the file for certain text that would only appear if the player was online. If that text is found then it will return a rendered image (GD tools) that says the player is online, otherwise it will return a rendered image saying the player is not online. it's simple in concept but for somebody who's never seen it before, the script seems pretty ingenious to me. I'll probably design a PHP version of this in the future, just for practice and good measure
And specfically for hotstuff911, heres the code you might consider using
http://ilfirin.org/graal/gadgets/gst...t%20on%20Graal
all in an image tag