I have been to NYC countless times +just learned about this amazing place .
You go on organized profesional tours of different areas of these former tenement housing for families in late 19th century. it is fascinating to see the history with such detail. It is great for all ages above 10 .
There are multiple tours but we did Hard Times + Shop Life which were both excellent esp the former.
You can buy tickets online before which will save some time.You need to plan for this to see the tours you are interested in.