If you can code, compile, and test your applet following these instructions, the applet will look like this in your browser:
If you do see the applet then your background knowledge and your system setup are ready for you to begin the course.
If you do not see an applet that looks like this you probably need to download the latest JDK version from Oracle.
You can find a link to the download page at Oracle from
Java Resources page.
Follow the installation instructions provided there.