Visa requirements:
Citizens from any EU or Schengen Area country need only a valid National Identity Document or passport to enter Spain. Citizens from other countries may need a visa (or a valid residency permit or a valid long-term visa issued by another EU Member State).
Please check this page and the entry requirements and procedures. The nationalities requiring a visa are listed in Annex I of Regulation (EU) 2018/1806.
If you need a visa, you can apply for it at the Spanish embassy or consulate in your country of residence, please contact the organizers to get an invitation letter.