See the Getting There section of the main page for directions to the trailhead.
From the trailhead, follow the well-marked trail (marked with large posts) that traverses up the hillside on the west side of Hekla's lower slopes. The route goes up to a low saddle and then turns left into lava fields to gain the ridge. Once on the ridge, the marked posts end and you will follow the trail up through a breach between high points on the ridge. You will pass a crater on your left. Traverse slightly right through a lava field to gain the trail again on the right of the ridge. Follow the ridge up to the first false summit and stay on it continuing to the second false summit and finally the actual summit. The ridge is broad with snowfields but non-technical.
Not sure about the distance but it took me 3 and 1/2 hours to ascend and about 2 to 2.5 hours down. Elevation gain is 3200 feet.
None needed but be prepared for bad weather which blows in constantly.
If you have information about this route that doesn't pertain to any of the other sections, please add it here.