I would study the past simple at first. It is the easiest of the past tenses to understand and to start to use immediately. Find yourself a table of verbs, especially the irregular verbs (as they are often used the most) then you look at the past form. Regular verbs end in either -d, -ed or -ied. Irregular verbs have to be learned as they are different. Then the construction is just the subject (I, you, he/she/it, we, you, they) and the past form of the verb. That's it!

Most past tense sentences are constructed using a past tense form of the verb or a helping verb. For example if you wanted to say "I drive my car" in past tense, You would say "I drove my car." or "I have driven my car."