Not able to connect due to incorrect WEP question.

Have Lion and using Airport Extreme. Connecting Sony TV to wirelss internet. Sony gave me these instructions:

1) Launch airport utility

2)log into airport accesspoint/router

3)choose manual setup

4)choose the wireless icon

5)change the wireless encryption type - Apple is normally set at 40bitWEP and needs to be changed to 128bitWEP.

6) clcick update to save changes.

I have been in to airport extreme utility and don't find what I am looking for. Anyone able to assist?

Thanks!