Yes! You only need one Skylight Plus subscription for all of your frames. There is no limit to the number of frames you can link to a single Plus subscription.
Please note that your Skylight Plus subscription is linked to the personal email address you used to purchase it. To automatically link your frame with your Plus subscription, you will need to use that personal email address during the registration process.
If you plan to register your frame with a separate email address, simply register the frame, sign into your account at app.ourskylight.com, select your email in the upper-right corner, and visit our 'Link your Plus Account' page.