If you have Roku or Fire stick, check out the NewsOn app. Most of the local stations also have streaming apps for those devices, as well as smartphones and tablets, where you can watch the live news broadcast or replay an earlier broadcast.
As far as over the air, your TV needs to have a digital capable tuner - almost all TVs made since the late 2000s will. Depending on your location you may need an amplified DTV antenna, and there's no guarantee of signal strength or availability. Most of the local stations don't seem to have many active repeaters any longer, so coverage is spotty.