how to add java and html is easy.. the first question is to where are you trying to add it? the main page or the right hand boxes?
the right hand boxes would be the more common - to do this got to edit design and copy and paste your code into the box that you wish it to appear in
To the main page Id suggest putting it into a table but this makes the process a little more dificult.
The basic point for this is open the page that you wish it to be displayed in the editor
Click source then copy and paste the code into the appropriate area of the page.
If you are uncomfortable using the scripts or code Id go with the right hand box option as it automatically apears on every page and there is little editing that needs to be done.
Hope this makes sense