Navigate to Administration | Customize Window Layouts. Select a layout that you would like to customize | Click Edit Button | Right click the field you want to set as Required and select Properties from the pop up menu.
Selecting the Properties option will open a window displaying the properties of the selected field.
Checking the Required check box will designate this field as one that is required. A small red asterisk will be placed next to the field in the window denoting the requirement. The record will not be saved unless all required fields have been completed.
