We use the present perfect tense to talk about things that started in the past and may or may not continue into the future. To form this tense, we use the auxiliary verb (helping verb) have plus the past participle of the main verb.
have/has (not) + past participle
I have traveled to Italy. He has talked about this issue more than once. Have you called your mother this week?
We haven't eaten lunch. She hasn't written any books.
Forming the past participle
The past participle form of regular verbs can be formed by adding -ed. There are no rules when forming the past participle form of irregular verbs. These must be memorized. I've provided a short list of commonly used irregular verbs below.
Download List of Irregular Verbs here.