Alta Airport (IATA: ALF) receives direct flights from Oslo (SAS and Norwegian), Bergen, Tromsø, and a few other Norwegian cities. Flying is the standard way to arrive — the road from Tromsø (about 3.5 hours) is the alternative for those driving, but Alta is a long way from anywhere.
From the airport, taxis and local buses cover the short distance to town. Car rental is available at the airport and useful if you plan to explore the surrounding region or visit the rock carvings at Hjemmeluft.