The following is a summary of the WPSSO Core Pro version installation process.The complete and detailed installation instructions are available here.
Updating to WPSSO Core Pro is simple and easy — click on the “Purchase Pro Version” button on any SSO settings page. After your purchase, an email will be sent to you with a unique Authentication ID and installation instructions.
The WPSSO Core plugin and its Pro add-ons use the WPSSO Update Manager (WPSSO UM) add-on to check for Pro version updates. If you haven’t already installed the WPSSO UM add-on, please see the WPSSO UM download and installation instructions here.
Once the WPSSO UM add-on has been installed and activated, enter the unique Authentication ID in the SSO > Licenses settings page. After saving the changes, an update for WPSSO Core will appear on the WordPress Dashboard > Updates page. To install and activate the new Pro version, update the plugin from within WordPress (as you would any other plugin).
If you use a WordPress multisite configuration, you may enter the Authentication ID either on the Network SSO > Licenses settings page (to license several sites at once) and/or in the individual site / blog SSO settings. Note that the default site / blog must be licensed to allow Pro version updates from the Network admin interface. This is a requirement of WordPress not WPSSO — WordPress uses the default site ID to manage updates in the network admin interface.