To start, you will need to have the device you want to cast and your TV connected to the same Wi-Fi connection.
From the drop-down settings in your phone, you will need to turn on "phone visibility" or simply select the cast option.
Depending on the phone you are using, you may need to activate your phones "smart view" or equivalent function. This enables the device to locate any other unit to sync up and share content.
Please note, if your phone is in a power saving mode, the phone will not allow the Screencast functions to be performed.