The imperfect tense of 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 tener (to have) as an example:

ten + (ending) --> tenía, tenías, tenía, teníamos, teníais, tenían

The first and third person singular forms are identical, therefore the context must distinguish between the two. Let's look at some example sentences:

Yo tenía el derecho de paso.
I had the right to pass.

Tú tenías las llaves.
You used to have the keys.

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

No teníamos tiempo.
We didn't have time.

Let's look at some other verbs.

querer - to want
Yo quería ser doctor.
I used to want to be a doctor.

Tú querías resultados.
You were wanting results.

Todos queríamos viajar al mar.
We were all wanting to travel to the sea.