Open the Field Setup dialog box (double-clicking that field in the Database Explorer window or using the Field Setup command), select the Special > Default value option and enter the desirable value which can be:

• For numeric fields: any unformatted number.
• For text fields: any text string.
  If that text field is formatted as "Date", the default value should represent the generic date/time string: YYYY-MM-DD.

Select a range of fields and/or records and use the Insert > Default Value (Ctrl+T) command. Default values are inserted into all empty fields within that selection.