To reach the trailhead, I recommend using a mountain bike or taxi. I paid $9 for a taxi from Hanga Roa, but this required a bit of Spanish. By using a taxi, you can walk all the way back to Hanga Roa by way of the West Coast, which is very scenic.
From Hanga Roa, mountain bike, hire a taxi, or drive from Hanga Roa. Follow the road towards Vaita, which begins near the International Airport. Turn north at the good gravel road marked for Ahu Akivi and follow the road to the site. You can't miss the trailhead, as there are seven huge moai statues at the trailhead! This place is 8kms/5 miles from Hanga Roa.
From Ahu Akiva, find and locate the track heading east by backtracking along the road south for about 20 meters/70 feet. I actually headed east too early and had to climb over a few fences, but the fences are meant to keep horses, not hikers out. Once you locate the correct track, follow it northeast through the pastures. 4wd’s do drive this route to the summit, but there isn’t a road, only a faded track in places. Since the country is open, it is easy to see the way to the summit. Just head towards it. The slopes are gentle and grassy. The route curves north and reaches the summit. You can also visit the crater lake of Rano Aori which is southeast of the summit and near a large forest of eucalyptus. Return via the same route.
Once a week, a jeep tour comes up here, so try not to do the trip on that day. I had the summit and hike all to myself and it doesn’t seem like much people come up here at any other time. Return to Ahu Akiva. Round trip is about 9 kms/6 miles.
Once at Ahu Akiva, you can walk back to Hanga Roa, assuming you used a taxi to reach the trailhead. My map shows a fairly direct track or trail that heads to Hanga Roa via the area east and south of Maunga Roiho, but this is not the route I took. I headed directly west and passed north of Maunga Roiho. There were some old 4wd tracks and horse trails at first, but the route become more rugged closer to the coast and crosses some rough lava fields. Along the way, I found two huge lava tube caves and a large carving of a swordfish(?). I really am kicking myself for not bringing a spare battery for the digital camera on the hike. No tour groups make it out here, nor are these places ever mentioned in the books, so it was really thrilling to just stumble on them. Good luck if you find them. You may find something else as well. After crossing the rough lava fields, I met the coast just north of a ranch with a large cross. You then follow the track along the west coast south to Hanga Roa. This was something like 3-4 miles from Ahu Akiva to Hanga Roa.
You can also use the main track farther north than my route that heads northwest from Ahu Akiva and then meets the coast. You then head south to Hanga Roa. This route also passes some huge lava tube caves and some more interesting sites. It is longer than the route I took, but since you are on a gravel track, it may be just as fast.
There isn't much shade, so sun protection is needed. A good pair of boots is needed as well.