Access Youtube from your browser or open Youtube app on your Iphone device; after that, coppy the video URL you wish to download to clipboard.
Paste the the copied video URL into the search box of SaveTheVideo, tap the red Download button. You also can enter keyword to search videos on Youtube.
Now Select the format you wish to download then tap "Get Link". After a few seconds, you can download the file from appeared download link..
If your Apple device is not jailbroken, it cannot download media other than from Itunes. In such cases copy download link and use free Documents app to download video file and save to your device.