Purchase a TV converter compatible with Mac (see Resources). Some TV converters won't work with cable or a Mac, so read the description of the product well. Consumer Reports keeps unbiased and thorough expert reviews about hundreds of products. With specific questions, call your local Apple Store or electronics store.
Remove your new converter from all its packaging and place it in a convenient place close to your computer. Plug in the power cord to a wall socket. Plug in the cable sending TV information to your television into the corresponding hole in the back of your converter. Turn on the converter.
Open "Finder" on your Mac. In the top of the left panel you'll see all the discs and objects currently linked to your computer. Double-click the one that says "TV" or "TV converter" to open it with a video program.