Your TV will work with the regular remote features straight without any setup, but to use the microphone you will first need to pair the remote with the TV.
Press and hold the 'left' and 'home' buttons simultaneously on the remote until the indicator above the microphone button starts blinking green.
Next, open Settings > Accessories in the TV's menu.
You will see the TV remote - simply select it and it will pair with the TV, enabling the voice control and microphone features.
The voice control can be accessed with the Google Assistant or microphone buttons, as highlighted in the images below.