You'll need to see whether you have the SWM wiring setup or the older 2 wire setup. How to tell? Glad you asked. If you have an HD receiver or DVR just press the <dash> button right below the 7 while you are watching normal TV. If you have the new single wire setup, it will say "SWM Connected" in the pop up box. If it doesn't say it, you have the older setup.
If your box is an SD DVR, check and see if you have 1 or 2 cables at the Sat In ports. If you are SWM, then you will have just a cable at SAT 1 and SAT 2 will be empty.
If you have just a SD receiver, you'll need to check for a little red filter at the SAT-In port or locate your SWM Power Inserter. That's a little black box about the same size and shape as a chalkboard eraser with 1 green light on it. It will have 2 coax connections on one end and a power cable on the other end. If you have these on your system then you are SWM.
You could also check the label on the bulb at the end of the arm on the satellite dish and if it has a green label, you are SWM.
If you have a SWM you need to get a SWM Splitter or SWM multi switch. You can get them from Amazon or better yet, www.solidsignal.com. If it's not you can just use a Splitter, but make sure it is a satellite splitter and not just a regular cable splitter. If you can make sure that any barrell connectors are orange inside instead of white, you'll get a more reliable signal.
Better yet, just have DTV install it.