Finland is a party to the Schengen Agreement, which allows people to move freely within the Schengen area (all the Nordic countries and the EU with the exception of Great Britain and, Ireland and Cyprus). Accordingly, anyone entering Finland from within the Schengen area needs only a valid passport or some other official document issued for travelling purposes. Students coming from outside of the Schengen area will need a passport and possibly also a visa.
Check the list provided by the Ministry of Foreign Affairs of Finland to see if you need a visa in order to enter the Schengen area.
If you need a visa:
Contact the nearest Finnish Embassy for further assistance.
Mark it in your online application and upload a scan of the first page of your passport to your application.
Make sure that your visa allows for a few travel days both before and after the Summer School session.