Looking for a train route from Helsinki to Narvik.

There is no direct train from Helsinki to Narvik; head towards either Kemi (multiple trains a day, including both day and night trains) or Tornio (3 night trains a week), travel to Haparanda by bus, take the train to Boden and switch to a train to Narvik. You will probably have to spend a night somewhere (Luleå might also be an option - it's only a small detour). 

If that's too complicated: Take an overnight ferry to Stockholm, spend some time in Stockholm and from Stockholm a direct night train to Narvik. 

There are no trains from Narvik to Bodo, but there are buses.

Nice, do you know the buses that would do those travel. Can't find them

Just use Google.

https://reise.reisnordland.no/assistant?filter=bus%2Crail%2Cexpressboat%2Cferry%2Cairportbus%2Cother&searchMode=now&fromId=NSR%3AStopPlace%3A62318&fromLon=17.441289&fromLat=68.44151&fromLayer=venue&toId=NSR%3AStopPlace%3A58952&toLon=14.390518&toLat=67.286621&toLayer=venue