We form the present perfect with the present tense of the auxiliary verb have and the past participle, e.g. Pete has finished his homework.
Use of Present Perfect Simple:
- for actions which happened at an unstated time int the past. The exact time is not mentioned because it is not important
Kim has bought a new house
- for actions which started in the past and are still continuing in the present
She has been a teacher since 2001.
- for actions which have recently finished and their results are visible in the present.
They have washed their car.
- with today, this morning etc. When these periods of time are not finished at the time of speaking
She has typed four letters this morning.