How to Make a Field on the Names/Matter Screens Required

Go to the Screen Designer window be clicking File > Setup > User Preferences.
In User Preferences window, click the Appearance tab, and then select the Names or Matters button.
Highlight the screen that you want to edit and click Edit. This is the Screen Design Window.
In the screen design window, locate and right-click on the field that you want to make required.
This will open the Field Properties window.
In the Validation Condition field type the text – !empty()
This will tell the program that data is required in the field.
Save your changes and exit