Go to the Salesforce AppExchange listing for PK4Connect and click the "Get it Now" button. Select the relevant option to install it in your Production, Sandbox, or a Developer Salesforce org.
Indicate that you have read and agreed to the terms, and click the Confirm and Install button. If prompted, enter your Salesforce login credentials.
Choose whether you would like PK4Connect to be installed only for Admins, for all Users, or for specific profiles, then click the "Install" button. A dialog appears, for permission to approve third-party settings. Select "Yes, grant access to these third-party web sites", then click the Continue button. Once PK4Connect is installed in your org, you will see a Done button - click it. PK4Connect is now installed in your Salesforce org.
Click the App Launcher and click the PK4Connect tile to see all the tabs related to PK4Connect. You can now start using PK4Connect for sending mass emails to the recipients in your org.