Need a bit more info, exactly what brand/model of antenna and TVs do you have, are you sure you are in range of signals and does that antenna you have work with the type of signals in your area? Are your TVs ready for digital signals, are you in the US?
Did you select over the air and run channel scan on the TV after connecting the antenna? Digital TVs will only access channels found when you run the scan.
Did you try reorienting the antenna and repeating the scan?
You may need a rooftop antenna.
You may need a better indoor antenna.