If you want the same validations to be performed for both actions, you don't have to do anything. As Prasanth pointed out, you just define the validation rules for the form and the validations will be performed for both actions.
If you want the validation rules to be different for each action, do the following:
Have your ActionForm extend ValidatorActionForm instead of ValidatorForm
In the validation.xml file, specify the action path rather than the form name in the <form name= > stanza.