You get to use the free offer once. Only one one-year offer is available per family, regardless of the number of devices purchased. If that was your question?
Here’s how to redeem it:
Turn on your new Apple device and sign in with your Apple ID.
Open the Apple TV app. Make sure your device is running the latest version of iOS, iPadOS, tvOS, or macOS.
The offer should be presented immediately after launching the app. If not, go to the Apple TV+ channel page where you’ll see the offer.
Tap Enjoy 1 Year Free.
https://support.apple.com/en-us/HT210573
Your subscription is for Apple TV +
Apple TV + is Apple Original content. It’s a channel found within the Apple TV App. The shows included in your subscription will have the tv+ logo on them
You can watch on multiple devices signed in with the same Apple ID you subscribed with
Devices you can use with the Apple TV app and Apple TV+
https://support.apple.com/en-ca/HT210740
If you have Family Sharing, up to 6 family members can watch on their devices
Set up Family Sharing
https://support.apple.com/en-ca/HT201088
Set up Family Sharing in the Apple TV app - Apple Support