the easiest way is got there by bus starting from Narvik
. To Narvik you have a train connection from Sweden.
The bus takes 4:30h, three bus departures daily - two each on Saturday and Sunday.
Some useful links for traveling by bus:
To go further to the North
, continue using a bus:
to Alta (7h), then you have to stay there for a night and continue to Honningsvåg (7h) and then to the Nordkapp (North Cape): 45min.
My opinion: don't do it during your interrail tour (you loose a lot of time) - do it when traveling Scandinavia by car.
More information here in the forum: