Step 1:
Choose one of the games in the gamelist that you want to watch and click on "View".

Step 2 (only once):
After you clicked on "View" you will be asked to download a file.
Don't save it but rather select "Open with ..." .

When you start the client for the first time you will see the java loading screen and after it has finished you have to accept the license (If you don't want to do this every time you should activate "Always trust content from this publisher").

Step 3:
Now you will see the gui of the client. You can activate or deactivate player / observer chat and you can choose wether you want to see which hero skills the players selects - in real-time. At the beginning of each game the client has to buffer some data so that the game won't lag later. When the client is ready you will see the message "Ready! ..." from that point on you can proceed as you would with the normal client: join the game via local area network games in Frozen Throne. To get a list of the in-game commands just type "/help" in-game.

Notes:

The Web Client doesn't have IRC support (yet).
If you are using Opera, you might want to take a look at the Opera web client HowTo

In case you don't have the Java runtime you can download it from the SUN HP.

If you have any questions, please post your questions in this forum!