Learn the present perfect tense: it indicates an action in the past, but with a present effect.
Compare the following sentences:
e.g. I reported to the police. (past tense)
e.g. "Why don't you call the police?" "I have reported to the police."(present perfect tense)
In the first example, the action took place in the past, e.g. "yesterday."
In the second example, the action also took place in the past, but the past action has a present "implication" or "effect"; that is, "I don't have to report to the police NOW, because I already REPORTED yesterday. So the present perfect tense is: past action + present effect.
e.g. The patient has died.(it's TOO LATE to call the doctor)
e.g. He has messed up our plans. (that is why everything is a mess NOW)
e.g. I have watched that movie. (I don't want to see it AGAIN)
e.g. The crime rate has gone up in Chicago. (the crime rate is STILL GOING UP)
Compare the following:
e.g. Many people die from cancer. (present tense, indicating a FACT)
e.g. He messes up our plans. (i.e. he is a trouble maker all the time)
e.g. My dog watches the door at night. (it stays close to the door every night)
e.g. Food prices go up with inflation. (food prices and inflation go hand in hand)
Next time, I'll talk about past tense and past perfect tense.
To learn more about tenses, read my book Effective Writing Made Simple.