Depending on how old the programmer is you'll need to plug it into your computer to get the most recent updates (i had to do that).

Then it's under the "advanced options" menu.

There's only one receiver for the rear of the vehicle. I forget how it knows left vs right tire... i think it has to do with signal strength. Could be that the left rear TPMS sensor is getting weak, so the module thought it was the right tire (the receiver is on the passenger side, so the right tire would normally give a weaker signal than the left due to proximity)