Picture in picture (PIP) is a convenient feature of many televisions and digital cable set-top boxes. Rather than having to choose between two different programs on two different channels, PIP opens one channel in a small box in one area of the TV screen while leaving another channel displaying on the main TV screen. How you control it, or even whether you have it, depends on the make and model of the digital cable box that Comcast installed in your home. With some basic troubleshooting, however, you can learn your cable box's PIP functions.
Examine the remote that Comcast provided you and look for a PIP button or a section of buttons that are physically separated from the others with a PIP heading. A typical set of buttons that would be used to control PIP functions would be "On/Off," "Swap," "Location" and separate channel up and down controls for changing the channel on the PIP screen alone.
Press the "On/Off" of "PIP" button to activate PIP. You should see a small screen in one area of the TV; if so, you can manipulate PIP by changing its channel independently, moving it around the TV, etc.
Contact Comcast customer support for further assistance. Depending on what make and model of cable box Comcast installed in your home, you may need to activate PIP functions in one of the box's internal menus before you will be able to use it. Alternatively, Comcast may have installed a box that does not feature any PIP functions and you will need to upgrade in order to get the function.