Samsung Galaxy Note 2

How do I change the signature line on yahoo mail on my Samsung Galaxy Note 2? It currently states the following: Sent from Yahoo! Mail on Android. In Yahoo Mail Mobile app, there are no settings for changing the signature line.

If I go into the generic email settings (i.e. which looks like an envelope with a red circle and @ in the middle, I can change this to something else but it doesn't recognize the yahoo mail mobile app.