Past Indefinite Tense:
Past indefinite tense is used to express that action was done inthe past time.
girls sang a song.
Structure for imperative sentence:
Subject + Verb (2) + Object.
Structure for Negative sentence:
Subject + Didnot + Verb (1) + Object.
Structure for Interogative sentence:
Did + Subject + Verb (1) + Object
For Further explaination checkout the video below.