I assume you've spent a lot of time basically being told to eat small amounts and do cardio. If that's the case, I'm going to tell you the exact opposite: Eat more and lift heavy (for you) weights.
I'd set a 6 month goal of gaining that 10lb. That's roughly 2lb/month, 1lb/fortnight, 0.5lb/wk. That'll mean eating 250kcal/day more than it takes to maintain your bodyweight. Training burns roughly 450kcal/hr (as a very rough average -- you could burn much more or much less than that), and I want you to train 3-4 days/wk, so to average things out you're going to increase your current energy intake by 500kcal/day. I want that 500kcal to come from an additional 25g protein (from meat, eggs, dairy, grains and legumes or a protein shake if needed), 10g fat (good fats, like olive oil and omega 3's, not trans fats) and 75g carbs (whole grains, fruit, vegetables and milk, not cupcakes and ice cream).
For your exercise, like I said before, heavy weights, 3-4 times a week. Heavy isn't defined by an arbitrary number, but by your own physical limits. RPE (rating of perceived exertion) is a good measure here to figure out if the weight is heavy or not. By the end of a set, a light weight should be an RPE of 0-5/10; a moderate weight 6-8/10; and a heavy weight 9-10/10. You'll actually be starting off with light weights at the beginning of your program, but as you establish good technique you'll gradually add weight to the exercises, and in time you'll move up the scale into moderate and ultimately heavy weights. Once your technique is good, you'll want to spend most of your time at 8-9/10 RPE, basically stopping 1-2 reps short of failure. Put technique above progressing the weight, but don't spend the next 6 months avoiding progression altogether, either. Your goal is to get all your reps with good form. If you get 9/10 reps with decent form, you can increase the weight used. If you need to cheat to finish a set, then the weight's too high for your current level, so back off a bit. Here's a basic 3 day/wk resistance training program I've prepared earlier:
http://training.fitness.com/weight-training/basic-novice-program-strength-muscle-54545.html
If you want to train 4 days a week, make it an upper/lower split:
Upper Body Session:
- Bench Press (or horizontal push variation) 3x10
- Overhead Press (or vertical push variation) 3x10
- Lat Pull Down (or vertical pull variation) 3x10
- Row (or horizontal pull variation) 3x10
Lower Body Sessions:
- Squats (or knee-dominant variation) 3x10
- Deadlifts (or hip-dominant variation) 3x10
- Calf Raise 3x15
- An abdominal exercise for the front and an abdominal exercise for the sides (there's a lot of options here) 3 sets
In this instance, take on a schedule like Mon Upper, Tue Lower, Thur Upper, Fri Lower, and rest the other 3 days.
Do that for 6 months. Get to a point where you can squat 60kg and deadlift 80-100kg. Follow the guidelines I've given your for diet, and assess whether you need to adjust calorie consumption based on how much weight you gain each month (remember, you should be gaining 2lb/month) and, more importantly, how things are going in the mirror. Once you get to that point, you should be at 120lb with improved body composition. If you've gained more fat than muscle (although that shouldn't happen for a beginner following the advice I've given you here), then it's time to cut the excess fat. Report back at that time and we'll give you information on how to get rid of excess fat without losing the muscle you've worked so hard to build (I'll give you a clue, you still want to be lifting heavy weights when cutting fat).
Please keep us updated as you progress along, so that we can continue helping and supporting you!
