Determine whether you need to obtain a Finnish tourist visa by going to the Ministry for Foreign Affairs of Finland website. EU residents and U.S. citizens generally do not need to pre-arrange a visa and can simply present their national ID card (EU residents) or valid U.S. Passport at the border. This entry stamp is good for 90 days, after which you must leave Finland.
If you do need a Finnish tourist visa, find your nearest Finnish Mission on the "Finnish Missions Abroad by Country" page (see Resources). Contact the Mission during normal business hours for a list of visa requirements.
Bring the requested documents, along with your passport and the visa fee, to your local Finnish Mission, or hire one of the many visa arrangement services to process your visa. After two weeks, your visa will be ready.