Hi, I'm traveling to HK for the Christmas break and would like to go to Macau for a day.

You should first prepare the required documents including proof of financial support, the application form, a passport-style photo, copy of your passport, flight itinerary, hotel reservation, and your travel plan. Next, submit the application to the embassy of China in India to apply for it.
Or if you think it is challenging, you can find an agency to help you apply for Macau visa.