Apply rules for Data validation

Select the cell(s) to use and choose Data >  Data Validation.

Choose an option in the Allow drop-down menu, such as Date or whole number.

Under Data, choose a condition like equal to, and values to accept. 

To add a prompt, enter a title and message for your rule on the Input Message tab.

Choose Error Alert to create an invalid data entry message, and select OK.

Select the cell(s) to use and choose Data > Data Validation.

Choose an option in the Allow drop-down menu, such as Date or whole number.

Under Data, choose a condition like equal to, and values to accept. 

To add a prompt, enter a title and message for your rule on the Input Message tab.

Choose Error Alert to create an invalid data entry message, and select OK.