hhoope01

You can redeem online or via phone call to MR. If you make a reservation where the cert is usable, the system will try and pull that cert, or if you already have a reservation without a cert attached, you should be able to access the reservation online and tell it to use an existing cert.

If you aren't too familar with the online tool, a phone call may be your easiest option, but the online isn't too hard to figure out either (in most cases this is true, but once in while it really is easier and better to just call.)