Beta tests - how to?

Hi, I've heard women talk a lot about beta testing - I just got a faint positive pregnancy test, but have had 2 early previous miscarriages and am feeling more anxiety & fear than excitement.  I would be very interested in having these tests done, especially because my OB suspects I may have low progesterone.  Do I just call the office to set this up?  How does it work?  Thank you.