So, all you need to do is remove the Winegard power supply wall plate. On the back side, remove the "Cable" Coax from wall plate and connect that to the A side of the A/B switch. Connect the satellite output to the B side and run a coax jumper from the single A/B output right back to the Cable connection on the wall plate.
As mentioned earlier, you will need to get the RF modulator for the receiver with will provide you with the necessary coax output to run to the splitter. At this point either the satellite output or Cable will go to your TV's when you power off the Winegard power supply (wall plate) depending upon whether you select A or B and OTA TV signal will be sent to the TV's when the power button on the Winegard power supply is on no matter what the position of the A/B switch.
Does that make sense?