How to build size and muscle for soccer while working on endurance?

I am trying to become a professional soccer player in the MLS. I am 20 years old and I am a very good soccer player but the problem is that I am currently too skinny (135lbs)... I am the type that has trouble gaining weight through eating. The goal for me is to reach 160-170lbs. How can I pack muscle and size, and at the same time work on endurance/speed/etc.?