How to save someone's Facebook video onto my iPhone?

One of my friends uploaded a video onto their Facebook page and I'd like to save it onto my iPhone. I use the Facebook app.

It will cost you 99¢ but download the "Downlaods" app from the App Store. It has a green icon with an arrow facing down.
Play the video in the app and click download.
Then you can email to your computer or keep it on your phone.