To change your video quality On Smart TV's / Media Streaming Devices, follow the steps below:
If you're using an Android TV / Amazon Fire TV Stick / Xiaomi TV:
1. While watching a video, tap any arrow key on your remote, or the pause button to bring up the player controls
2. Select 'settings' (Cog icon) on top right corner
3. Select your preferred Video Quality under the Video Quality section
If you're using a Samsung TV / LG TV / Vewd TV / Sony CEB TV:
Unfortunately, selecting a Video Quality isn't an option on these devices currently. It will play the best possible quality basis the speed of your internet connection.