To add new validation to the page, open the Server Behaviors Window:
Window -> Server Behaviors
Then double click on the Server Validation server behavior. Select the type of validation you wish to use, then click the lightning bolt next to server variable and select the form element you wish to validate, then click the plus button tp add the validation to the list. Click the help button in the server validation wizard to get context sensitive help.
Again, on the server behaviors, you can double click the insert record server behavior to bind you new database columns to the new form elements.