Where can I obtain information about this for obtaining an approval as a Production Organisation (POA)?

Below are two useful links regarding applicable regulations, guides and information needed for POA processes:

• AESA link for National POAs: 
  https://sede.seguridadaerea.gob.es/sede-aesa/catalogo-de-procedimientos/aprobación-de-organizaciones-de-producción
• EASA link for POAs EASA: 
• https://www.easa.europa.eu/document-library/general-publications/easy-access-rules-initial-airworthiness