How to download Youtube video to IPhone for free?

Okay I really like a video that there's only 1 so how do I save it to my phone?

Download iTube! It's completely free (Unless you get the pro version).
How to use:
1. Go to the 'Search' tab (Down the bottom)
2. Search what you want.
3. Find the video you want.
4. Wait until the bar at the top is fully orange (Which means it is downloaded)
5. Enjoy your video!
-Thanks for reading,
Blake

Very simple, here's a vid tutorial for you!