Good advice. but what i'd add, seeing as you said you're skinny is to start off with strength training. something like stronglifts 5x5. start with just the bar to begin with. It will allow you to work on your form. Eventually you will be lifting very heavy weights.
I used to be very skinny i didn't even fix my diet to begin with. But following this program slowly just made me fix my diet and now alhumdulillah, although not the biggest of guys, i'm of decent size and i'm stronger than most people at 24/7 gyms.