This article has some great ideas for improving your overall nutrition:
Three good meals and some snacks everyday, plus a good workout shake. It's a basic plan, but it works just fine.
At your age and size, this is totally not an issue to waste energy thinking about. You're fine. Even based on your picture, it's not a major deal.
Joe DeFranco's Westside for Skinny Bastards was specifically made to add quality size on high school and college athletes. Check it out:
Dan John's Mass Made Simple would be another kind of size plan. Dan has a ton of experience working with younger athletes: