Lesson 52 introduces the use of the root Hay Yod Hay as the equivalent of ("there was").
In Hebrew there are three uses of the verb for of this root:
1) General use (The house was big [no equivalent in present tense])
2) Existence/occurrence of an event (There was a party here [there is a party here])
3) Possession (There was a book to me [there is a book to me])
This lesson provides example to practice the second use of the verb (Existence/occurrence of an event)
Past tense rules to express a thought about existence of an event in the past tense, are similar to present tense rules (see lesson 6). ("Yesh").
One thing to pay attention to is avoiding double negative (don't use Lo and Ein). Ein should not be used in past tense. To translate there was not........, people should say "Lo HaYah".