Now days the TV needs to be a digital TV. If not you will need a digital to analog converter.
In the menu for the TV be sure the input is set to antenna, air, or over the air. This will allow the TV to use the antenna to scan for channels. As you travel down the road the channels will disappear as you get out of their broadcast range so you may have to do some manual tuning to find something to watch.
You may have a bad antenna connection make sure all connections are tight.
To prevent all of this you can get Dish or DirectTV which are satellite based services. With an in-motion sat dish antenna you would be able to pick up TV source as you travel.