I've never done it and I'm doing this from memory so hopefully I have it right.
Turn off your RC. Flip over the drone and find a flashing light on the underside. That light also acts as a button. It's a bit tough to press but you should be able to reach it with a pencil or something. Anyway press it in for a bit. I believe it either changes color or flashes at a different rate or something (I forget). But once that's done it's set up to re-pair. Turn on the RC and they should link up.