With a three-input modulator, you can program a third video source, like a satellite television system, VCR or DVD player, to be available for viewing on Channel 74. Make sure you keep the channels you create at least two channels from existing cable or UHF stations. Plus, you'll need one empty channel between your modulated channels. Each modulator has a specific range of channels to which the signals can be programmed. After mounting the cameras, you'll want to route the camera cables to the modulator, usually located at the cable or satellite system point of entry.
Most cameras have separate video signal cables and power cables.
Connect the video signal cables to the inputs of the modulator, and connect the power cables to a power source. Depending on your comfort and skill level, you may choose several methods of getting the camera cable inside your home. Most cable and satellite dish installers will simply run the cable along the outside of the home, securing the cable with wire clips. A hole is drilled in the wall for the cable to enter. You could certainly use this quick and simple method, but be sure to caulk the entry point of the cable to keep spiders and other uninvited guests out.