If the school got you the flat they can fill out the documents for the building you are staying in and turn them in. But if you are renting on your own the owner/s of the flat must take their passports (in person) and your passport and the completed documents to the housing office and get the document stamped, pay your taxes for the length of your visa then you or your school must turn this packet into OVIR (all within the 3 day time period of course). This seems to be strict in Moscow but I'm not sure how strict it is in St. Petersburg or if it is even a requirement in other parts of Russia.