On GTA4, How Can I Start The "Courier Service" Achievement?

Question

I was looks through the achievement list and saw this one, what is it and how do i start it?

if it helps, i have completed thee Story Mode.

Answer 1

Once little Jacob trusts you enough, he will offer you work on the side. Once you finish each work mission, you'll get the achievement, and a really sweet ride!

EDIT:

just noticed that you said you completed the story mode. Okay, since you've finished the story mode, bring out your cell phone, choose phonebook, then choose Little Jacob. Choose job and he'll tell you what to do.