Grammer

how do i tell the simple past tense apart from the past continuous tense

The main difference between past simple and past continuous tense is that:

we use past simple tense when something happened at some time in past. We also commonly use this tense with past time adverbs (yesterday, last night, two days ago, etc.)

For example: John called his friend yesterday.

we use past continuous tense if an action occurred in the past and lasted for a period of time.

Example: I was reading a book all day yesterday.

We used past continuous tense because the action of reading lasted for some time (a whole day in this case).