Yes or No

Highlight the cells

This example shows you how to display a drop-down list so the user can only select Yes or No.
Select the cells you want to apply this restriction to. In this case

Enter the Criteria

Display the Data tab and find the Data Tools group.
Press Data Validation to display the Data Validation dialog box and select the Settings tab.
Select List from the Allow drop-down list.
Enter the text "Yes,No" in the Source text box.

Press OK to apply the data validation.