how do I do AirPlay from videos on my laptop to the AppleTV connected to my Samsung TV?

RRRoss,

Thank you for taking the time to explain. The Apple TV app on your Samsung TV is an app that you can access from the Apps section of your Samsung Smart TV. You can learn more about Apps on your Samsung Smart TV here:

Apps on your Samsung smart TV

Your Apple TV is a separate device that connects through an HDMI port on the back of your TV. You need to select the HDMI input that corresponds with that port to view the contents of your actual physical Apple TV. It isn't possible for the two to merge. You may need to contact Samsung support for assistance with finding details about how to select external HDMI devices connected to your Samsung TV.

Contact Us | Official Samsung Support

Good luck!

Hi, RRRoss.

Welcome to the Apple Support Communities. We’re glad you decided to reach out about mirroring your videos from your laptop to your Apple TV. We think these articles may help:

AirPlay system requirements - Apple Support

Note that your laptop will need to be a MacBook with macOS Mojave 10.14.5 or later, and your Apple TV will need to be either the HD or 4K version with tvOS 11.4 or later. 

Use AirPlay to stream video or mirror your device’s screen - Apple Support

Check the “Stream video from your Mac” section for direction.

All our best.