It sounds like you got an SWMLine dish, that is a dish that has a built in SWM module. There should be one coax coming from the dish into your house where it goes to the power interface, then a coax out of the power interface which is split and goes to your various receivers. This is a case where you can split a coax.
Right now you have a total of 5 tuners, 2 in the DVR and one in each of the regular receivers. The SWMLine dish is capable of supporting 8 tuners total, so all you should have to do is unplug the coax from the regular receiver and plug it into the SWM port (typically Sat 1 input port) on the DVR and you should get dual tuner capability. Assuming you de-activate the regular receiver, you will increase your total tuner count from 5 to 6 and could still support up to two more tuners.
Carl
Right now you have a total of 5 tuners, 2 in the DVR and one in each of the regular receivers. The SWMLine dish is capable of supporting 8 tuners total, so all you should have to do is unplug the coax from the regular receiver and plug it into the SWM port (typically Sat 1 input port) on the DVR and you should get dual tuner capability. Assuming you de-activate the regular receiver, you will increase your total tuner count from 5 to 6 and could still support up to two more tuners.
Carl