There's usually a manual in every package of a filter that tells you the technical details about it, and also how to set it all up
About cleaning it, you could open it up when you change the water in the tank and see how it looks. If it'll still be very clean, it might be good to rather start cleaning the filter every second water change. I clean my external one once a month or something... it's so full of media that it.. pretty much never gets dirty
Last time the water I rinsed it in looked like somebody had mixed a chocolate cake into it.