Genesys Cloud for Salesforce enables administrators to configure extension points using custom Apex classes to customize actions such as click-to-dial and screen pop functionality. The configuration process requires creating an Apex class that implements required interfaces, then navigating to Setup > Installed Packages > Configure next to the Genesys Cloud for Salesforce package, selecting a call center definition, and designating the custom Apex class under Extension Point Settings. Once configured and saved, the Genesys Cloud client executes actions based on the customizations defined in the Apex code. This functionality is part of the broader Salesforce call center setup series and applies specifically to Genesys Cloud for Salesforce integration, allowing organizations to tailor client behavior to their specific business requirements.