From Kenepuru Saddle, follow a steep singletrack to the ridge. Don't be fooled though as following the ridge is a constant up and down (enjoyable, but challenging at times). A steep descent will get you to the road. Cross the road to continue on the Queen Charlotte Track or take a right turn to roll down to the Bay.
Be aware that as of early 2017 (or even earlier) there is no facility to buy groceries at Portage anymore.
The Queen Charlotte Track is a multi-use trail that travels over DOC and private land. The trail is typically completed over multiple days. To learn about access, accommodations, and useful information check out this brochure, here.