After you rent a movie from iTunes, you can watch the rental on any Apple device associated with your Apple ID.
First, you need to find your rentals on iPhone, iPad, iPod touch, Mac, PC or Apple TV.
Now, you can download rental to an iOS device or computer for offline streaming. But you can only watch your rental on one device at a time. Make sure that the Internet connection is available before you start downloading.
You cannot download the same rental to more than one device at a time. So, if you need to switch the rental from one device to another, here is how to do:
Step 1. Delete the rental from the first device.
Step 2. Find the same rental on the second device and re-download it.