Have you bought “Recruitment” and “Custom Field Builder” both? I am not sure which one you have bought as you have written a mixed name.
Custom Field Builder and Recruitment are two separate add-on.
>> Custom Field Builder is to add custom fields to the forms of HR, CRM modules (As Recruitment works with HR module, so custom field builder can be used to add fields to Recruitment forms too)
>> And Recruitment is to manage the recruitment process.