sale / purchase of parking in housing society

I PURCHASED A FLAT IN PUNE WITH PARKING. THROUGH AN OVERSIGHT IN SALE DOCUMENTS THE ' parking " remained to be included. The previous owner has settled in BANGLORE AND IS TOO OLD. ACTUALLY , THE BUILDER SOLD THE FLATS FIRST [IE NO MENTION OF PARKING IN AGREEMENT ] LATER ON , ON COMPLETION OF BUILDING THE PARKING WAS SOLD ON SIMPLE ISSUING RECEIPT OF PAYMENT . PLEASE ADVISE ME W HAT TO DO TO GET THE PARKING CORRECTED