I believe you can run your data against the Ancestry (if that's who did your test) again and again. The results are based on who has been added to their database.
You can also download your data to other companies databases but I can't explain it further.
DNA Detectives is a good web site to explain DNA. I know there are also a lot of books about DNA and you can probably find one or more at your local, public library. Successful Searching!