The word have is a verb, meaning to be in posession of, or own or contain something.
So depending on your sentence, it would go like this:
I have a cat.
You have a cat.
He/She has a cat. (Notice that have changes to has for the he or she form)
We have a cat.
They have a cat.
Had is the past tense of have. It means you used to be in possession of, own or contain something, and you do not it anymore.
I/You/He/She/We/They had a cat. (It is the same for all of them)
Have been is more of a phrase using the above combinations.
I have been to Costa Rica. - This is used to show that you have gone somewhere or done something.