In English there are a lot of prepositions. However there are some common ones that we use to indicate time as well as other expressions that we have.
In the class presentation you have a chart that indicates that uses of the prepositions in, at and on which are the most common prepositions.
In your books besides those prepositions you have some other time expressions. Complete exercise 9 on page 27.

on:
ResponderBorrarSaturday.
Mondays
Mondays mornings
sunday afternoon
in:
the morning
the afternoon
the evening
the week
on:
week
day
month
morning
sunday morning
at:
nine o´clock
hafl past three
night
the weekend.