At / In / On

Ali, I hope this will explain some of the differences in usage between “at”, “it” and “on”

Definite location - I would like to meet you at the park tomorrow.
My son is at school now.
Exact Address - I live at 123 Main Street.
Events - I met her at the football game.
Workplaces - I have been hired to work at the drugstore.
I work at the mall.

Smaller location within a larger location - I am in my bedroom right now.
He is in his house now.
I live in Toronto, which is in Canada.
Supported by something - My cell is on the chair.
He left his coat on the floor.
I am walking on the sidewalk.
Approximate address - I live on Main Street.
Tom lives on the north side of town.
Public transportation - I am on the bus now.
Tomorrow at this time, I will be on the train.
Exact time - She went to see the doctor yesterday at one o'clock.
Let's get together tomorrow at 2.
Did you want to have lunch today at noon?
There was a lot of noise last night at midnight.
I wake up early in the morning.
We usually go for a walk in the evening.
Note: in the morning, in the afternoon, in the evening, but at night.
Months - I was born in September.
Judy was married in June.
Years - Were you born in 1991?
Columbus discovered America in 1492.
Seasons - I go on holidays in the summer.
In the winter I have to shovel the snow.
Days of the week - I don't work on the weekends.
He was born on the 23rd of June.
They always exercise on Fridays.
Special Days - They love to go out on New Year's Eve.
Let's get together on Christmas Day.