Either ride up Hedonism and straight across the powerline and up the bottom of the S Bomb. About 10 minutes up here (all rideable up), on the left, is a big wooden sign for Brokeback Ridge.
Alternatively switch onto this as you come down S Bomb.
It's pretty unlikely that you would find anyone whose Top 5 in Fernie does not include Brokeback. Bermed switchback after bermed switchback, fun flowy sections all on buffed single track with a few option dirt launches. Do it!