1. Enter Inbox in the Quick Find box from Setup then select Setup Assistant under Inbox.
2. Click Get Started if it’s your first time visiting the Inbox Setup Assistant.The Inbox Setup Assistant shows all the steps you need for Inbox deployment.
3. Click Get Package to install the Inbox Control Panel, (Alternatively, you can directly install the Inbox Control Panel from the AppExchange.)
4. During installation, select Install for All Users.