Translation:He lives in Warsaw, beside the square, on the ninth street.
The square in question is likely the Rynek Starego Miasta, the oldest square and market place, located in the centre of Warsaw's old town. At least that's what I'd refer to if I just said "square". :)
The streets are not numbered and it's hard to order them anyway, since there was no proper city design back when most European cities were built. So, this sentence is not really true-to-life. Just there for educational purposes.