I think it's quite clearly the second part of the title. If it was just "How to Win Friends" it might be something more people don't dismiss just based on the title.
"... and Influence People" makes it sound like that's the purpose of befriending someone, i.e. getting them to do what you want, or to do something for you.
"... and Influence People" makes it sound like that's the purpose of befriending someone, i.e. getting them to do what you want, or to do something for you.