Applying for Post Grad Work Permit Outside of Canada

[Ccs]

Hi, I was a student this past year in Canada, but after graduation moved back to the US while I waited for the college to finalize the diploma. Now I want to apply for the post-grad work permit but I'm unsure if I can do that while outside of the Canada. And if so, when I'm at the border will they ask for my student permit to trade it for the post-grad work permit?

Thanks in advance!