"I used to look at" would be said: miraba refering to a repeated habit from the past. The ending aba refers to the tense called "Preterito imperfecto" in Spanish, (imperfect past) which may be expressed by "Used to" in English.
In Spanish, this past tense tends to describe and action or event from the past which temporary limits are nor relevant.
The imperfect combines past tense (reference to a past time) and imperfective aspect (reference to a continuing or repeated event or state).