I think you need Audit result from your school. You should be able to download it from your school portal. You can use it to apply for PGWP.
Otherwise Google PGWP for students
He will apply as within canada, once he gets his passport back, he should go to the border closest to him to get his study permit document. also.make sure the border allows it
Hello, please where did you send your passport and how long did it take to get your passport back.
For your question, you need to go to the border to get that letter