To write in third person past tense, the writer needs to use third-person pronouns, such as "he," "she" and "they," and the writer needs to use past-tense verbs, such as "was." Pronouns are the words that replace nouns.
When writing in third person, the writer cannot use first or second person. First person includes pronouns like "I," "me" and "we." Second person is primarily using the pronoun "you."
Past-tense verbs discuss the action as if it were in the past, rather than in the present or future. For instance, the past tense of "jump" is "jumped" while the future tense is "will jump."