Hike up the Buffalo Fork 5 miles, and another 3 up the South Fork and put on below the final Class V rapid (right next to the trail). Some folks also hike in from the Angles Trailhead near Togwotee Lodge for a shorter hike. The South Fork is a classic packrafting run, featuring a Class IV bedrock drop and a great little canyon with some pinched moves to make. Paddle out 5 miles on the Class III Buffalo Fork, a nice run in its own right.
Video: Packrafting South Buffalo Fork at low water