Firstly a smart television requires an internet connection, either via wi-fi or it can be hard wired to your network router. Home plugs or network adaptors as there known can be used as an alternative and are mains powered, one at the TV end and one at the router end, both these are then connected one to the router and one to your television / media unit, the connection is then passed through the electric circuit,
The smart functionality varies from the different manufacturers, basically they don't all have the same apps. The most common are BBCI player, ITV X, All 4 and My 5, also known as catch up services, other popular ones include a web browser and usually You Tube, Netflix and Amazon.
The apps on the set are what you have, they are added or taken away by the manufacturer themselves, these and only these are what is used. Your broadband speed will need to be about 2mbs to stop buffering ( the playback slowing down and stopping ).
When all this is set up you can enjoy programmes that you missed usually over the last 7 days. Series are sometimes kept on the service a little longer but it can vary.
The featured image shows typical apps on the set ( these may vary ), click on the app you want, look for the programme you want to watch, sit back and enjoy.