To install sample data in Dynamics 365, go to Settings->Data Management:
Select Sample Data:
Click Install Sample Data:
You will see the message “Installation of sample data is processed in the background. You can continue to use Microsoft Dynamics 365”:
Close the dialog. Click to open it again. You will see the message when complete, “Sample data is installed on the system”. Note the option to Remove Sample Data:
Sample data will then be installed.