One of the more scenic rides in Sweden is the Innlandsbanan. The ride groes from northern situated Gällivare to Mora. Östersund is one of the bigger stops on the route and is the main connection point as trains between Trondheim and Sundsvall call at Östersund as well.
The inlandsbanan doesn't follow the coastline of Sweden but goes inland. The route is not profitable enough anymore for normal passenger traffic, so a few trains leave every week with the main purpose of transporting tourists through the hills and forests of Sweden.
Trains from Stockholm are frequent and also run as night trains. There is a "mid Sweden" line from Sundsvall and Nabotåget trains from Trondheim, Norway. Apart from that, the famous Inlandsbanan trains stop here in summer.
If you come by car, E14 is your road and Östersund also has an airport for flights to and from for instance Stockholm.