How would I go about becoming a childrens book illustrator?

Im currently a studio arts major college student and I was planning on having childrens book illustration as a potential career option for me. Problem is, I dont know the first thing I would need to do to prepare and go about this. I know I need a portfolio, and I can gather that up, but how do find a company? How do I send them my stuff? Any info and advice I would appreciate!

Oh, and if it helps, i live i fl, and im going for my BFA.