>I thought I have done it before and it was easy. But somehow I can't do it. Here are the steps I follow:
>
>1. Click on Setup
>2. Click on Twit Filter
>3. Then I click on Add.
>4. Enter the ID of the person but no record is selected.
>
>What am I missing?

The way I've done it is click on a person's name in the From: or To: sections of a message, and then on the user profile you have a Twit button on the toolbar.