Easiest way is using a gopro with the app installed on your smart phone.

The correct FPV way is to use a security camera/fpv camera with a 5.8 ghz video transmitter. On the receiving end, you'll need a 5.8 ghz video receiver with a monitor or a FPV headset from fatshark.

Gopro tends to lag a bit where as the set up above will have very little latency.