On facebook - I have a friend's list set up. But I can not figure out how to add existing friends to it.?

Well, follow these steps : 1) Login to your facebook account. 2) Click Account > Edit Friends. 3) Then, on the left side, look for Lists. 4) Click on the the list you ever create. 5) After the list appear, click edit list. 6) Popup will appear. Then, start to select the friends you want him/her listed on that friend list. 7) Save list. 8) I guess that you can see the changes on the list or when chatting. That's all. Ultimate Computer Learning (http://www.ultimate.cz.cc)

For adding existing friends, you can use the edit friends button the right side of the screen. If you need a straight forward guide, this video is pretty good: http://wp.me/pwR2N-jr 1 minute video on how to add friends to list who are already your friends.