This page is for connecting two Joomla sites as Master and Slave.
To get login from a Slave site using user credentials from a Master, you must have done a Usersync. To do a Usersync, you have to have the jFusion plugin Enabled showing on the jFusion cPanel in the Slave. To have that, you must have disabled User Registration in the Slave, by going to User Manager, Options, and clicking the Radio button, then Save.
It appears that you also have to have jFusion installed on the other (Master) site.
When you configure the Slave, the int_joomla is your local (internal) site, ext_joomla is the Master site. Remember when you are setting the database/connection parameters for the Master to use the Master's connection parameters.