Using SaveTube could not be more simple because it shares its interface's design with the original app. This feature is super useful because you can explore the content just as if you were using the YouTube app. Also, if you start the session using your Google account, you can browse the feed of the channels that you're subscribed to, so, the additional download option makes the official YouTube app practically obsolete.
In order to download any video, you just have to open the player, click on the arrow icon and set up the final download quality. Once you've done that, the downloading process will start automatically in a matter of seconds.