You need to add a small code to your HTML-Page containing the applet.
Because the applet will not run when Java is not installed - so you need to do it in a more "native" way.
So add the following to your HTML code (inside the body):
document.write('Java is enabled'); <!-- add the applet in here -->
document.write('Java is not enabled'); <!-- tell the user that it will not work -->
You can also test and develop it first without the applet.
That value in
can be extended and carry pretty much from a simple String, an image reference up to a applet with params...