What is the best way to rent (or buy) a movie and have it down load to my husband's Ipad?

I got him a Ipad or a notebook (OR WHATEVER!) for Christmas. Also got him a cable to hook it up to the TV so we can watch whatever on the TV. We’ve been watching episodes of Home Improvement all day, and I remembered the movie Wild America. He would LOVE that movie, but we don’t feel like getting out and renting it. (It’s dark, cold and snowing but at least it’s not muddy and we are not clumsy.)

So, what do we do? How do we do it?