How to add spouse name in the property registry !!

Hello, I have purchased a flat from a builder in Noida (U.P.). The construction is complete and is ready for registry. Initially when i booked the flat it was only my name in builder buyer agreement but now before the registry of the property I want to add my Spouse name as well in the registry. Builder is saying they have sent the list of allottees to authority. Can you please help me to understand the process for this, as how can i add the name of spouse now ? Thank you KK