Welcome to the site. I am guessing from your post that your main goal is to add some weight and muscle to your frame. I am going to give some general nutrition advice until we get some more details.

First thing is to make sure you are getting enough protein in your diet. If you do not get enough protein you will not grow, period. Aim for 1.5 grams of protein per bodyweight, so for this would be 225 grams for you. This may SEEM like alot when your first starting but it should be pretty easy after a while. You can get the majority of this from your shakes.

I didn't see any mention of protein shakes, do you take any? If not I would suggest picking up some from an online retailer as they are cheaper than the local GNC. (two of my favorites are BulkNutrition and DPSNutrition) Something like Optimum Nutrition 100% Whey is cheap as hell and good enough for most people. When you figure out what you like you can try other brands and protein blends.

Make sure you are getting a PWO (post work out) shake in immediately after your workout. Most people consume a shake that contains somewhere in the range of a 2:1 ratio of protein to simple carbohydrates. So get in at least 50 grams of protein (or near to it depending on manufacturer's servings) and aim for 100 grams of carbs. One of the easiest ways to get these carbs are from Dextrose (a type of corn sugar) which can also be purchased at the online sites. You can start low on the carbs say at 50 grams and work your way up to a level your comforable with, personally I find I can't stomach more than 75 grams and it works fine for me. The reason this PWO shake is so important is because you have a "window of opportunity" for you body to get in the extra protein to start repairing the damage from the workout and to absorb the simple carbohydrates to restore your glycogen levels.

You want to be constantly feeding your body. Aim for at least 5-6 small meals a day with each meal containing some protein. A good way to keep track of calories/protein/fat content is by using Fitday and using their food journal for a while. Since you seem like a pretty skinny guy your main goal will be to eat, eat, eat!

If you give us more details about your exact diet,for example post a sample daily meals, we can critique it. I just don't want to write a whole bunch of stuff that may not apply

In the meantime I would highly suggest checking out this article or searching our forums for general questions. The article will cover some basic macronutrient needs (carbs/fat/protein) and some great sources of these. Their is probally a whole bunch of crap you have never heard of in there, but slowly start applying the nutrition part of the article it should help. Also don't skip out on the legs! You will regret it later when your body starts showing its progress. Nothing looks goofier than someone with a nice upper body and twigs for legs.

If you need clarification on anything just ask. Didn't want to make this post too long.