Ok, basically as you know an applet runs as part of an HTML page.
If your applet is written using anything greater than or equal to Java 2 (so 1.2.1 and upwards), or if it is written using Swing components (identified by being preceded by a J e.g. JApplet, JPanel, JButton etc) then the HTML page must be converted before it can run in most of the common browsers.
The conversion program you have downloaded from sun helps you do this, but it must be the correct version for the release of java that the Applet has been compiled by:
all you need to do is run the HTMLConverter class file in the same way you would run any other java class file (obviously making sure you have access to the java command by setting up your PATH variable in windows properly).
If you run it a panel will pop up prompting you for the path and name of the HTML file you wish to convert. It also gives you the option of backing the whole lot up into another specified path if you wish. It also needs you to specify the type of conversion needed (for me this is always standard for IE and Navigator on Windows and Solaris).
and then once this is done hit the convert button and the conversion should run. You will know it has been sucessful as the screen tells you the number of applets it detected during the conversion process (of course this should be at least one).
That is basically it, once this quick conversion has completed you should be able to open the html page in a browser and the applet will load.
Hope this helps.... :