If you are a citizen of a so called third country, i.e. a country outside of the EU/EEA, you will need a residence permit for studies if your studies last for longer than three months.
You should apply for the residence permit as soon as possible, the processing time is usually longer during the summer months. Please note that you can initiate your residence permit application online, but you still need to visit the nearest Finnish embassy or consulate in person to submit the application.
You should also note that a health insurance is mandatory when applying for a residence permit for studies.
You can find more information on the residence permit and insurance as well as links to the Finnish Immigration Service on the New Students website. Please read the instructions and information provided by the Finnish Immigration Service carefully, a complete application helps the permit process on the way.