We use Present SimplePast SimplePresent Perfect:

• for a finished action which has an effect or result in the pastpresentfuture:

  I have sliced a cucumber. Let's put it in the salad;

• with such time adverbials as just, already, yet:

  She's already done her homework;

• for an action that started in the pastpresentfuture and is continuing into the pastpresentfuture:

  My grandma has lived in London since her birth. Her flat is in Hampstead;

• to talk about our experience in the pastpresentfuture without specifying the time:

  We've seen this film before. Let's choose another one.

The short form of "I have" is "I've""I'eve""I'd".

The short form of "she has" is "she'as""she's""she'es".