Syncing users between master and sub sites


I've bought the plugin "User Sync". The ultimate purpose of it for me to by the plugin is to sync the users between both master and sub site(s).

I created a new account on one of the subsite and after few couple of minutes, I checked on the master site, but I couldn't find the new user being updated. I want the users on both sites (master / secondary) to be synced vise-versa.

It's highly appreciated if you can assist me to fulfill the requirement and direct me how to do it.