If the sentence talks about the things happened or done in the past, then the tense is past tense. You can also identify it by some words in it like was, were, had, had been , or the Past Participle form of the verb.
If the sentence talks about thing that are being done or are happening in that moment, then the tense is present tense. You can identify it by some words like is, are, have, has, are being, or the present tense of the verbs.
If the sentence talks about thing that are going to happen , then the tense is future. You can identify it by some words like going to, will be, will have, the future tense the verbs.
