بودم

In a sentence

• من در مدرسه بودم.

  I was at school.

  The word "بودم" here functions as the past tense of 'to be' for the first person singular.

• دیروز خانهٔ دوستم بودم.

  Yesterday, I was at my friend's house.

  The word "بودم" here expresses existence or presence in a location in the past, referring to the speaker.

• صبح تا ظهر مشغول کار بودم.

  I was busy with work from morning until noon.

  The word "بودم" here describes the state or activity of the speaker in the past.