The past imperfect tense is used to describe actions that were habitually completed. Examples are: “I used to study”, or “I used to run” or “I used to work”

Here is an example with the verb “to go”

I used to go (masculine) : मैं जाता था

I used to go (feminine) : मैं जाती थी

We used to go (masculine) : हम जाते थे

We used to go (feminine) : हम जाती थीं

You used to go (to a person of lower status)(masculine) : तू जाता था

You used to go (to a person of lower status)(feminine) : तू जाती थी

You used to go (to a person of the same status)(masculine) : तुम जाते थे

You used to go (to a person of the same status)(feminine) : तुम जाती थीं

You used to go (to a person of higher status)(masculine) : आप जाते थे

You used to go (to a person of higher status)(feminine) : आप जाती थीं

He used to go : वह जाता था

She used to go : वह जाती थी

They used to go (masculine) : वे जाते था

They used to go (feminine) : वे जाती थीं

So to form the past imperfect, take the stem of the verb and attach it to either ता (if the pronoun is singular, masculine), ते (plural, masculine), or ती (feminine, singular, plural). Then you’ll need an auxliliary verb depending on whether the pronoun is masculine, singular (था), feminine, singular (थी), and so on.