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If we are speaking of the result of a past action rather than of the action we must use the present perfect tense. When somebody says, I have seen Panthenon, he or she is not thinking so much of the past act of seeing it, as the present result of that past action.
Use the past participle (and not the past tense) with the auxiliary verb have and its parts.
Don't use must and ought to as past tenses. To express a past duty (which wasn't done) use the perfect infinitive without to after ought to or should, or expressions such as had to, was obliged to.
In indirect speech use must and ought to as past tenses: He said he must do it.
Don't use the past perfect unless there is another verb in the past tense in the same sentence.