Not a lesson

Just jumping in here to echo other comments: This lesson alone is not a lesson, it just tells you that this tense exists.

Thanks to another commenter, I'm studying these two lessons to learn how to conjugate in imperfect tense:

Conjugate regular -ar verbs in the imperfect tense in Spanish (El Pretérito Imperfecto)
Conjugate regular -er and -ir verbs in the imperfect tense in Spanish (El Imperfecto)