downloaded .jnlp won't open

[John O Laoi <brianolaoi@gmail.com>]

I am using squeeze.

To join a webcast, I download a .jnlp file.  (  I  am using Iceweasel)

When it is finished downloading, a pop-up box offers me to open it
with "Sun Java 6 Web Start (default)".

I accept, and then I get  a number of errors, with the heading
"Application error  -  unable to launch the application"

When I enquired with the supplier, I was told that I need
 to have the Java Runtime Environment from www.java.com installed.

I am probably trying to open the .jnlp with the wrong Java.

Questions:
How do install the java from  www.java.com using aptitude?

How do I ensure that this is the Java that is automatically chosen
from within Iceweasel to open .jnlp file?


John