As Slovenia is a Schengen country, the rules and regulations about requiring and obtaining a Visa are the same as for the other Schengen countries. A list of countries whose nationals need to be in the possesion of a Schengen visa you can find here: ec.europa.eu.
For guidance about obtaining a visa for Slovenia please refer to the official webpage of the ministry of foreign affairs: www.mzz.gov.si
Shortly we will also prepare a detailed guide for obtaining a Visa specifically for our event.