I just enrolled and with my first bill I got a return this certificate and I can B1G1
free. Is there anyway to do this WITHOUT having to mail this?

Yes. Go here, look at post #883 and pick a "B1G1" code from one of the many listed, click the "Offer Details" link and then click the BLUE "Looking for the offer in your mailing" link. Enter the code in the box and apply.

But... you would do better to wait for a B1G1/Free ship combo to come up.