What will happen at the border?

[americanadian]

I am an American citizen, and I know that I will get a letter of approval from the Visa office, then I will take that with me when I psychically go to Canada. The border crossing will give me the study permit there. But when I pull up, do I tell them I need to get the study permit, like, how do I go about handling that? How long should I expect to be there for? Is it a relatively painless process at the border since I will have the letter from the Visa office? Thank you.