Foreign nationals intending to study in Croatia must regulate their temporary residence for the purpose of studying if their stay in Croatia is longer than 90 days. International students are not allowed to attend classes at university until they have procured a residence permit.
Nationals of countries subject to the visa requirement also need to procure an entry visa for Croatia (Viza C). Information on countries subject to the visa requirement can be found on the web site of the Croatian Ministry of Foreign and European Affairs.
The visa application (Viza C) must be submitted to the diplomatic mission or consulate of the Republic of Croatia in the foreign national’s home country. The visa application can be submitted either in person or via e-mail. A list of missions and consulates is available on web site of the Croatian Ministry of Foreign and European Affairs.
More at: http://www.studyincroatia.hr/living-in-croatia/student-residence-permit