Eat a lot more food. Shit, double your portion size on everything for a starting point. Eat a lot of lean meat, fruit, vegetables, olive oil, nuts, and every carb you can get your hands on. Milk is your new best friend.
Read the stickied threads on how to put together a balanced workout program.
What Gaz said.
Protein: consume 1-1.5g per pound of lean body mass (you don't need to provide protein for your fat mass).
Fat: minimum 0.5g per pound lean body mass (I like to do about 1g per pound LBM)
Carbs: fill in the rest as you see fit
Milk may be your best friend, but eggs will now be your God. Eat lots of them.
For training, focussing on major compound movements at relatively heavy loads will produce the best size and strength gains. Lifts like squats, deadlifts, bench press, military press, clean variations, rows, pullups/chinups, lunges, etc, will do you good. You can read through the stickies and try to put your own together, or you can choose from many reputable strength programs like 5/3/1, Starting Strength, 5x5, Westside, 20 rep squat, etc. Although, if you're looking for some bodybuilding with strength (which all of those will give as well) a really good program is Built's "Baby Got Back" program -- a great combination of power work, rep work, endurance work and compounds and minor yet well-placed isolation work. It will make you big but strong and functional as well.
