You select the cleansing package in the data cleanse. Inside IS you can modify the rules/data dictionary for that cleansing package, and republish. During the duration the CP is publishing, it is not available for use. 
I've been trying to find a link to the doc Im referring to, but Im having some issues finding it. I dont see it in the install directory either. Its 170 pages and goes over each component of setting up a CP. I'm working off a printed copy of this section.