Step 3: Nutrition
In your diet, you will need more carbohydrates, protein and calories. Carbohydrates give the body energy, proteins enable muscle growth after a workout, and more calories in general means (more energy as calorie is a unit of heat) your body will gain weight (and if you do it properly, it will be mostly muscle).
Don't be tempted to think that this means gain weight in any way (through fast food and other fatty foods). If anything, you must be even more conscious about your diet than before you started working out. Your increased carb intake should come from breads, pasta, rice etc (preferably whole grain, whole wheat, and wild rice where possible as these carry other benefits as well (fiber, vitamins etc.) )
Proteins should come from (if possible) from lean animals in one form or another. If not, though beans and nuts also have a lot of protein.
Fish - Very high protein to fat ratio
Chicken - Similarly high
Lean meats - Where possible eat the leanest meats to avoid putting on fat
Egg - High in protein (if your family has a history of high cholesterol avoid the yolk)
Milk - Quintessential. If you don't love it, you should learn to love it. High protein and almost no fat.
Yogurt - Similar to milk, though slightly more fatty
Cheese - VERY fatty although there are leaner cheeses with a lot of protein and little fat
Soy Beans - Probably the best thing for vegans to eat, enormous amounts of protein
Beans - Likewise
Nuts - In moderation, because like cheese they are VERY fatty
Your calorie intake should increase as you increase consumption of these good proteins and carbs. Don't ignore the fruits and veggies either, they have a lot of vitamins and fiber as well.
I'll expand from this overview in the next update.