The little icons you see next to programs in the application manager are PNG files.

Now copy a PNG into the resource folder. Start in your Wireless Toolkit folder (SprintPcsWTK?) and find the "apps" folder. Now find your application. Then look for a "res" folder and put the PNG in there like this:
C:\SprintPcsWTK\apps\FooBar\res\example.png.

Now set the application properties. Start KToolbar and open your application. Select the "Properties" button and then the "Optional" tab. You should see a property named MIDlet-Icon. Edit that property and change the value to "/SendNote.png".

Now package and deploy your application. Select the "Project" menu in KToolbar and then the "Package" option. You should get a JAR and JAD file for your application in the "bin" folder. The PNG image will be embedded within the JAR.

That should be it. You'll see the PNG graphic next to your application in the application manager.