question about Twitter app or Twitterrific app.

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Hi to all on the forum I have a question about how to use the originalTwitter app or Twitterrific I don't know those apps allot just to basic use but couple days ago I talked to some one on my list of following and this contact want to follow or subscribe to some list who I am subscribed and to be honest I don't know how to add to this list, some one else added to me at this list dot's y I don't know how to do it. could some one help me on this way. I use twitter app, Twitterrific, Chicken nugget or just the twitter clients .