See this information below which was copied & pasted from the Sky Store FAQ.
How many devices can I use to watch Sky Store?
Can I watch on more than one device?
Buy & Keep The movies and TV shows you buy at skystore.com will be available on all your registered devices. You can register up to four devices and watch on any of them. Once you reach your device limit of four, you can swap an existing device for a new one. You can make one change a month.
If you have Sky TV, you can send your Buy & Keep movies and TV shows to your compatible Sky box. Your Sky TV account must be linked to your Sky Store account. You can do this easily at skystore.com. Here's how: 1) Sign in to your Sky Store account 2) Click on your name in the top right hand corner to go to 'My account' then scroll down to 'My Sky account' 3) Click 'Link My account' on the right hand side and fill in the necessary details
Rent If you rent a movie on your Sky box, you can only watch it on that box. If you rent a movie on your registered device, it'll be available on all your devices but you can only watch on one at a time.
