Eligible candidates must live in Toronto, hold Canadian citizenship and be at least 18 years of age.
The information session is being held at the Etobicoke Civic Centre from 7 to 9 p.m. Staff will be explaining and answering questions about the appointment process.
Holyday left council after winning a seat in the provincial legislature in a recent byelection. He had been serving as the deputy mayor until his departure from Toronto City Hall.
While Mayor Rob Ford had wanted to hold a byelection in Etobicoke Centre, council voted in favour of an appointment process.
Click on the video above to see a full report from the CBC's Jamie Strashin.