There is a lot of good info you need to know, and it's really difficult to get it all into a this reply. I'm going to give you the condensed version. I'm going to start with the workout, then I'll get to the diet. The whole thing is as easy as, you have to eat more calories than you expend.
I've been using the 5 day split, with one free day routine. this means I train 1 muscle group each day, then on the sixth day I train what I feel in need more work on; day 7 means rest day. You can really decide how often you want to work out, but for weight gaining purposes, I suggest no less than 4, 5 days being the best. Like Dignan said compound lifts: squats, deadlifts, bench press, overhead press; then you should also give some extra love to the biceps and triceps. while the compound lifts will work the arms, you want to me sure to give an equal distribution to all body parts. Have you ever seen the guy at the gym with huge arms and chest, and itty bitty legs. Looks funny, right? He forgot to train all body parts equally. You will need to find somebody to show you proper form, because you want maximum benefit, and not hurt yourself. A knowledgeable friend, or personal trainer will be your best bet. if you do get a trainer, do your homework on the person, there are good trainers, and there are BAD trainers. I run a progressive system, where I try to add a little weight each time I work out, even if it's for just one set. I go 7 sets of 4-8 reps on big lift, then 3 sets of 4-8 reps on my smaller lifts. I go heavy, 75-80% of my max, and rest 2-3 minutes between sets. This has worked great for me, I have gotten WAY stronger, and added at least 25lbs of muscle in the last year (currently 6'3" 256lbs). Cardio should be put on hold, it just burns excess calories, and with heavy lifting, you will be burning enough already. I you want me to lay out a 4 or 5 day split for you, let me know. When it comes to sticking to a workout routine, it helps to have support, so drag your girls with you!
Now comes the tricky part, the diet. what you are looking to do is known as bulking. not in the traditional way bodybuilders do, but similarly (mainly minus the steroids). when you are trying to gain weight, CARBS ARE YOUR BEST FRIEND!!!!! they will help you recover faster from your workouts, and give your body the energy to build the muscle you want. The macro-nutrient breakdown for adding weight is to get roughly 30% of your calories from protein, 50% from carbs, 20% from fats.
Carbs: potatoes, sweet potatoes, brown rice, quinoa, whole grains (whole grain bread), oatmeal.
Protein: chicken, turkey, fish, lean red meat.
Fats: avocados, nuts (almonds, cashews, pecans, walnuts), healthy oils (olive, coconut, avocado).
an example as to exactly how many calories you need to eat to gain healthy is as follows. I took some liberties when entering your stats into the formula. I put you at about 13% body fat, so at a 10% calorie surplus, working out 4-6 hrs a week, you need about 1896kcal per day. that would break down as 105g of protein, 289g of carbs, 32g of fat. Now, this is in no way 100% accurate, I would need some specific stats to get it really right. if you use the my fitness pal app, and enter all the foods you eat, you can get a breakdown of all the macros. Protein shakes can help, I use them as part of a high protien/high carb meal after my workout.
Lots of people say you need to eat smaller, more frequent meals every 3 hrs, blah blah blah. That's just over complicated BS. It's all about total daily/weekly caloric intake. a little more, or a little less every day will not make any noticeable difference. You only see the difference if you go WAY over or under the caloric goal. dont make it more complicated than it needs to be. I also recommend that you don't get on the scale more than 2x per week, really you should pick 1 day a week and that's it. obsessing over each pound gained or lost on a daily basis on brings frustration. weigh gain and loss are not linear. you will go both up and down, you just try to go further up than down. If your goal when making these changes is to feel better about yourself, then obsessing over the slightest weight fluctuation will be counter productive.
If this whole thing didn't scare you off, and you really want to make some changes, I'm happy to give you some advice or resources to accomplish your goals. Unfortunately it's tough to fit it all in this little message box. shoot me a PM if you want more info.
FUCK, that was a long ass reply! Dignan gave some good info on this thread as well, it looks like he has a pretty go grasp on this too. We just differ in a few of our philosophies, and approaches. Everyone is different, and responds differently to different things. I just know what works for me.