For paid jobs at Spanish Administration such as CSIC you should first check the procedures for recognition of Professional Qualifications (Regulated by Directive 2005/36/EC) and Recognition of foreign Higher Education qualifications (equivalent to Spanish university Grado or Máster degrees) that give access to a regulated profession in Spain.

For employment offers you can visit http://administracion.gob.es/ or the CSIC homepage http://www.csic.es (training and employment). All offers for CSIC centres are published here.

Once a call is opened, you have to complete an application form and send in your CV provided with credentials (true copies of degrees, contracts, publications, training, etc.). 

Please check the document "Research career path in Spain at a glance" to see funding possibilities in Spain