Now that you have the package installed, you need to mount it somewhere. If you only have one instance of the acs-subsite package -mounted (the "Main Site") you can mount it anyhwere under +mounted (the "Main Site") you can mount it anywhere under that package. If you have multiple instances of acs-subsite, you can mount an instance of Directory under each subsite.
When listing users, the Directory package will find the nearest subsite above it on the site_nodes tree. It will then list