1. Present perfect tense

2. Use of Present perfect tense
Unspecified Time Before Now
Duration From the Past Until Now (Non- Continuous Verbs)

3. Unspecified Time Before Now
We use the Present Perfect to say that an action happened at an unspecified time before now. The exact time is not important. You cannot use the Present Perfect with specific time expressions such as: yesterday, one year ago, last week, when I was a child, when I lived in Japan, at that moment, that day, one day, etc. We can use the Present Perfect with unspecific expressions such as: ever, never, once, many times, several times, before, so far, already, yet, etc.
Examples:
I have seen that movie twenty times.
I think I have met him once before.
There have been many earthquakes in California.
People have traveled to the Moon.
People have not traveled to Mars.
Have you read the book yet?
Nobody has ever climbed that mountain.
A: Has there ever been a war in the United States? B: Yes, there has been a war in the United States

4. Duration From the Past Until Now (Non-Continuous Verbs)
With Non-Continuous Verbs and non- continuous uses of Mixed Verbs, we use the Present Perfect to show that something started in the past and has continued up until now. "For five minutes," "for two weeks," and "since Tuesday" are all durations which can be used with the Present Perfect.
Examples:
I have had a cold for two weeks.
She has been in England for six months.
Mary has loved chocolate since she was a little girl.

5. How to form the present perfect
To make the positive present perfect tense, use:'have' / 'has' + the past participle
Make the past participle by adding 'ed' to regular verbs (for example, 'play' becomes 'played')
There are a few verbs that change their spelling when you add 'ed' (for example, 'study' becomes 'studied')
We also have some completely irregular verbs
Examples:
I have played.
You have worked.
He has written.
We have travelled.
They have studied.

6. How to form the present perfect
The negative is really simple too. Just put 'not' after have or has.
Examples:
I have not eaten breakfast today.
You have not been to Asia.
She has not played tennis.
We have not slept all night.
They have not tried the food.

7. How to form the present perfect
To make a question, put 'have' or 'has' in front of the subject.
Examples:
Have I missed the bus?
Have you visited London?
Has it been cold this week?
Have we arrived too early?
Have they studied english grammar before?

8. How to form the present perfect
As you can imagine, for 'wh' questions, we just put the question word before have or has.
Examples:
Where have I left my umbrella?
What have you done today?
Why has he gone already?
What have we done?
Where have they learned english before?