At some point you'll notice what feels like a direct connection between your throat and the note. Every little nuance of throat motion is reflected in the sound. Then put some vibrato on the note by pulsing the air stream with your throat. The pitch will change up and down because you've got a hold of the bend with your throat. Often it is good to emulate what singers do, and start a note straight, then add vibrato toward the end of the note.
Some players think there's no such thing as too much vibrato, they love it that much.
Other players like to use it more sparingly, to add variety and contrast. I think you should use it a lot, but not all the time. Throat vibrato is one of the best things you can do to improve your tone, your control over the notes you play, and your focus on the connection between your playing and the response of the reeds.