Starting at Piney River Ranch, take the easy, flat and often overcrowded trail along the river for about 2.8 miles.
Once you back towards the waterfalls, there will be a fork in the trail marked by a large cairn that can EASILY be missed. This is where the fun begins. Get ready for about +1600 feet of gain over the next mile. Once you come to the plateau, there is an awesome camp spot with a little creek running though it.
Scramble up and over the pass (+1100 feet of scree). Up and over this pass gives you options to summit Mt. Powell which will be the mountain directly north of you. For Bubble Lake, continue down the valley for about a mile. After a mile down the valley, you'll come to a point where the south side (your right) opens up with a grassy slope. Stay high, scramble up the chute. Up and over this and you'll see the Bubble Lake.