Because the purpose of the walkthrough is to illustrate validation, the nature of the reservation is not important (for example, if could be for a restaurant, a community center meeting room, or something else), and the page does not actually process the reservation.
To add validation rules to a table, you open the table and use commands on the Fields tab of the ribbon.
Typically, your database is easier to use if you use IS NOT NULL and enter a friendly message in the Validation Text property.
You can use wildcard characters in your validation rules.
To add validation rules to a form, you open the form in Layout view and add rules to the properties of individual controls.
The steps in the section Add a validation rule to a table explain how to add validation rules to table fields.