If you'd like to watch TV using your battery, you need one of the following:
1. A TV that is designed for 12 Volts. It will have a "cigarette lighter" plug.
-or-
2. An inverter which converts 12 Volts Direct Current (Battery Power) to 120 Volts Alternating Current (Wall voltage).
If you want to go the inverter route, you'll need to get one with enough wattage capability to run your selected TV. For example, if your TV operates at 140 Watts, you'll probably need an inverter with a minimum of around 200 Watts.
Needless to say, either the 12V hookup, or the 120V hookup with an inverter will drain the battery, so you'll need a method to keep it charged.