Present perfect - 1

The Present Perfect Simple expresses an action that is still going on or that has stoped recently, but has an influence on the present. It puts emphasis on the result.
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 California, 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.

For regular verbs, in the Present Perfect Simple use has/have + past participle (verb + ed).
For irregular verbs use the list of irregular verbs in this link (third column):irregular verbs