We use already to say that something happened sooner than expected.

I am sorry, she has already gone home.
The film has already started.
She's only four years old and she is already reading.

Already usually comes before the main verb or between an auxiliary or modal verb and the main verb.

We use yet in questions or negative statements to talk about things that we expected to happen before now.

Have you finished the work yet?
I haven't seen the film yet.
A: Have you met him? B: Not yet.

Yet usually comes at the end of the sentence.

We usually use the present perfect with already and yet.