In your link, all you need from it is v=rky7JDeK4lo, then you change the equal symbol to a '/' to make it look like, v/rky7JDeK4lo. That is all you're going to need to have the Youtube Video on your profile, meaning you won't need the entire link.
For it to replace your Profile Picture on top you must first go to your "Edit Your Details" on your User Control Panel. From here, you scroll down on the screen until you reach the area where you put in your Video URL (which is what I mentioned to do above). Right below this you'll see "Swap Video" and you must select yes. This is where you can change the video to be your new Profile Picture rather than a regular image.
