How do you put a purchase movie from iTunes into the iCloud

You can't. iCloud does not store movies. The movie should be in itunes on your computer. If it's a matter of running low on free disk space, the itunes library can be migrated to an external drive (google this for instructions).

You don't actually have to move it to the cloud. If you delete it from the iPad, it is stored in iCloud for you so that it can be downloaded again from the purchased tab of the iTunes Store. As long as movies are included in the iTunes availability where you live, you will be able to download it again for free.

You can check here.

iTunes in the Cloud and iTunes Match Availability - Support - Apple

Another thing to consider is that if the content that you want to download again at a later date is no longer available in iTunes, then you are out of luck. I still use iTunes to transfer all of my purchases into my iTunes library and ultimately, this is what Apple recommends as well.

How to transfer purchases into your iTunes library

http://support.apple.com/kb/HT1848

After the movie is in your iTunes library, you don't have to worry about the possibility that it will be pulled from the store.

If you want to delete the movie, you can go to the movies tab of the videos app, tap the Edit button - and then tap the X on the movie icon in order to delete it.