I am trying to find out how to get tested to make sure that he is my real father and what I can do to put him on my birth certificate!

Most likely you will not get to add him to your birth certificate, but you could make a claim against the estate claiming to be a child. DNA testing would have to be done.

If your father left you shares in the will, that may not be possible either

More background would be helpful. Why do you think he is or isn't your father?

Also why is this important?

In many parts of the world... just being a child does not entitle one to a portion of an estate... particularly if a will has been drafted.