1) Diet = important. Eat 5-8 meals a day, and snack all the time. If you are skinny you more than likely have a high metabolism. Eat eat eat.
2) Training - try to do reps between 8-12 per set. So for curls try 3 sets of 8 with enough wieght that it is difficult and see how it feels. Remember to work your legs, they are your biggest muscles and will help your gains. Squats, deadlifts, etc.
3) Try to get your protien intake up. At your weight shoot for about 150-175g of protein (just my opinion) to start with and see how it works for you. You need a good amount of clean carbs in there, and do not neglect your fats (Omega's).
Try to provide as much info as possible for the guys here. Height, weight, calories, what you have access too, what your goals are, etc etc. There is a wealth of knowledge on these boards and you can often find a lot of it through the search tool, but posting exact info will spur the guru's to offer up more advice and suggestions.