Present Perfect

We normally use the Present Perfect when we want to talk about about something which happened in the past but is relevant now. Often we use words like just/already/not ...yet with the Present Perfect.

I feel really tired. I've just finished my report.
I haven't spoken to Brian yet but I've already spoken to Malcolm.

We also use the Present Perfect to talk about an imprecise time in the past but as soon as we become precise we switch to the Past Simple.

I've never been to Australia. Have you ever been there?
Yes I have. I went in 1992.