If you are traveling from Lower mainland (Vancouver), take Highway 3 East to Castlegar and then turn on to 3A and follow the signs.
From Calgary and points East, travel on Highway 3 to Creston. Here you have the option of traveling up the arm of Kootenay Lake to Crawford Bay and then taking the ferry to Balfour. From Balfour, continue west along 3A to Nelson. Your second option is to continue along Highway 3 from Creston over the Kootenay Pass to Salmo. At Salmo turn north and head on up to Nelson.
From Spokane, simply head north through Metalline Falls, cross the border at Nelway and continue on up past Salmo to Nelson.