Adding second drive to Optiplex 360

I have a second SATA h.d. that I'd like to install for backing up the primary drive. I see that the primary drive has another connector at the end of the cable. The second hard drive has a blue cable already attached to it. I am assuming that the primary drive connector is a power cable and the blue cable on the second hard drive is a data connector that connects to the system board SATA 1. Am I correct? Once the hard drive connectors are in place I think I go into the BIOS and set up the second drive. But I'm not sure how to do that? Please advise. Thanks.