If you have an Apple TV 4th Generation (newest version), you can download the Tubi app directly from the app store. You can find step-by-step instructions below:
- Open the App Store from your Apple TV home screen.
- Select Search.
- Type in "Tubi". The Tubi app will be displayed in the search results
- Select Tubi.
- Select Install and you'll be all set!
If you have a different version of the Apple TV, you can use Airplay to stream from your iPhone, iPad, or iPod touch to your TV. You can find more information here: How to Airplay to my Apple TV.