For your certificates to be recognised, you must address a letter of request to Spain’s Minister of Education, Culture and Sports:
Recipient: Sr. Ministro de Educación, Cultura y Deporte. Secretaría General Técnica. Sección de Convalidaciones de Estudios Extranjeros no Universitarios.
You may also submit this request at the Regional Delegations of the Ministry of Education, Culture and Sports (MECD), at Spanish diplomatic offices abroad, and through means provided in Article 16.4 of Law 39/2015, of October 1, on Public Administration and General Administrative Procedures. More specifically, the aforementioned law indicates that you can submit your request:
If you reside in Catalonia, Galicia or the Basque Country you should reach out to competent local institutions to seek the homologation of any foreign school leaving qualifications you hold.