How you connect your device to your TV varies from device to device and from TV to TV. 

For Apple devices we suggest using Apple TV

For Android devices we recommend Chrome Cast

Here is an article you might find helpful: 

For Apple TV:

To use AirPlay to watch your videos on your TV using Mac, iPad, or iPhone.

To watch videos by using AirPlay:

-Make sure your Apple TV is set-up

-Make sure your Apple device is logged on to the same WiFi network as your Apple TV

-Open the video on your Apple device and click on the AirPlay icon.

-In the pop-up that appears, select the desired TV and the video will begin playing