Flight
Can fly straight to Rovaniemi, or to Helsinki then take the train from Helsinki. Many other airlines also fly to Finland. Icelandair, KLM, Lufthansa...
Flight
Icelandair flies to Helinski with layovers in Iceland. A good option if you do not want to sit on a plane for 7+ hours.
Train
Students and seniors can get discount tickets. Train ride is typically the whole day or overnight. With an overnight train you have to add the cabin if you would like a bed otherwise it's just a seat.
Hotel