See if this helps with using the add-in for quantile column creation...I attached a few screen shots below.
This is my favorite way to do quantiles as you will have a ready quantile column created for anlaysis and graphing!
Once you identify the column, use the Set Cutpoints At Percentiles option from the Interactive Binning red triangle.
Then put in 10 to get every decile and put in the labels you want to see in the column.
Then use the Save Group Column to get the formula created back to your datatable!