The imperfect tense of a regular (er) and (ir) verbs take place by substituting the er and ir ending by ía, ías, ía, íamos,íais, ían.
Let's review the verb vivir (to live) as an example:

viv + (ending) --> vivía, vivías, vivía, vivíamos, vivíais, vivían

The first and third person singular forms are identical, therefore the context must distinguish between the two.

Let's look at some example sentences:

Cuando vivía en París me encontraba con él a menudo.
When I was living in Paris, I meet with him frequently.

Mi carro no tenía radio.
My car didn't have a radio.

Hace años no existía la computadora.
The computer didn't exist years ago.

Yo quería que Juan me ayudara a limpiar la casa.
I wanted Juan to help me clean the house.

No queríamos que ustedes se molestaran.
We didn't want you all to be bothered.

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