Changing the arm of a sofa

How do I change the arm of this sofa to match the photo. I am at a loss. I apologize, I do not know how to post topics on a community board either. Kagan Sofa.skp (5.2 MB)

You could try something like this

Kagan Sofa (SU 2017).skp (2.3 MB)

This is beautiful. Thank you so much. I am studying your Gif to learn how to do this in future. Thank you.