How can I put on some weight?

I'd take a look at this article written by Mark, it'll open your eyes to how to gain weight properly:
http://fitnessinventor.com/articles/652-how-to-gain-muscle-it-s-the-calories-stupid

Thanks Craig,
I will hopefully gain some weight soon enough!! :) Lets hope by the end of the first week! ;)
Thanks again.

As long as you train properly in conjunction with eating to gain weight, then the weight you gain will be the right proportions of muscle and fat. You need to ensure your muscles have a reason to grow; if you're tearing the fibres through resistance training then the food you eat can get to work building them back up stronger and bigger. You'll still gain the fat you want alongside this though to fill out the ribs so don't worry. My best advice would be to actually write out an eating plan based on the article above. That way you will always know what time you need to eat and what you're going to eat. It makes life so much easier trust me.

Good luck!

Yeah, thats a good Idea!! I will do that!
Thanks again for the advise!!