There are a bunch of these 4-button chargers out there. They mostly work the same with the same lousy instructions.
Tutorial: Tenergy TB6B Balance Charger for NiMH/LiPO/LiFe
Watch any variation of any charger that looks like yours, the Accucell-6 and IMAX B6 being a couple of the more common ones. You can search on those also.
Welcome to the forum and the crazy world of electric flight.