What do I do to get a flat and toned stomach?

Hi all:

I have been skinny all my life, I’m 5’8 and about 140lbs. My stomach is pretty flat but I want to tone it up. I don’t really do much exercise so I am not sure what type of things will get me results? Should I eat certain things as well? Thanks
Thanks guys, I don’t eat fast food or drink any type of pop, but my weakness is choclate. I’ll check out youtube for exercises :)