Where can I find the Endogenous Genes and Housekeeping Genes used for the Normalization of nCounter data?

This is found in the Quality Control section

Under the Quality Control tab, there is a graph for Variance of Mean that displays Housekeeping Genes for Normalization via blue dots and other Housekeeping Genes represented by yellow dots. You can also download this as a .CSV file if you would like to see a list with more information.