Check out the diet and nutrition forum to get your food in order.
You should not only choose to workout your arms and abs. You should workout your WHOLE body so you don't become unproportioned. Also, it would be pretty hard to stimulate growth by just working your arms and abs. If you are trying to bulk up, I would recommend a protein intake of 100-150 grams daily. Try to eat 5-6 small meals a day. You may have to force feed but that is how you see results. There's alot more to it than that, so read around and become educated. Good luck!