Ideally, a video switcher will have at least two devices connected into it. However, that is not a hard rule as there are many reasons why only one port might be connected permanantly. For example, maybe I only want a DVD player connected to this video switcher, but want the option of quick-connecting a digital camcorder to review video while avoiding the hassle of unplugging the DVD player.
Regardless, the video switcher will have a set of A/V cables going to the television and other sets of A/V cables going to external devices. It should easily rest on top of a television or on top of a device.
To add another device, repeat steps 7 and 8.