What is the significance of time in this story ? At what moments does the narrator mention time, and how do these instances contribute to the story’s overall effect?

It emphasized the time period and the devastation of the Plague called 'Red Death' which aftermath is death.

Explanation:

It emphasized the time period. The story relates a plague called the "Red Death"; it has long been devastating the country, and the narrator describes the process of the disease, emphasizing the redness of the blood and the scarlet stains. The disease is so deadly rapid that one is dead within thirty minutes after he is infected.

The story also emphasized the brevity of life, the fleeting of life and time, and the nearness of death, Poe reminds the reader that between the striking of each hour, there elapses "three thousand and six hundred seconds of the Time that flies."

the statement flat characters usually only have one trait that is developed in their story lines is true.