For server validation, you apply the validation to the page that the form posts to and then forward back to the original page if there are any errors. Then you would want to apply validation show if to error messages to display the error messages on the page that correspond to the validation.
If you don't want it to forward to a different page, you could have the action of the form be the current page and then forward after the validation passes.
You could also apply client side validation which will validate on the page and alert the user that there are errors.
