It is not possible to drive up to Riederalp, you must walk up or take a cable car. This walk starts from the parking at Ried-Morel, alternatively, you could start at Morel in the valley bottom and take the cable car from there. There is also a further cable car to the bottom of the Bettmerhorn but this misses out on the panoramic scenery as you walk above the Aletsch glacier.
(S) From the parking walk to the cable car station and take the cable car to Riederalp. Leave the cable car station and take the road through the town passing the supermarket with it on your right. Walk along the road passing hotels until the road takes a bend past 'Berghaus Toni' and you come to a signposted path.
(1) Turn right and follow the path contouring above the resort until you start to head uphill passing a barn on your left. There are many paths here but it is easy to navigate following the yellow signposts that mark the way. You are heading towards Blausee lake and the Bettmerhorn Bergstation. As a general rule follow the paths that head gradually uphill to the Blausee lake. (If you arrive on the ridge too early don't worry, just turn right and follow the path heading towards the Bettmerhorn)
(2) From Blausee pass the cable car and keep heading gradually uphill to arrive on the crest of the ridge with the Aletsch Glacier below you. This will be on your left as the follow the good path (Panorama Weg) towards the Bettmerhorn. You will arrive at a good viewing platform near to the Bettmerhorn Bergstation (cable car station.)
(3) At the viewing platform, enjoy the scenery and then take the path to the Bergstation.
You could eat your sandwiches here or there is a cafe in the Bergstation. There is also a free museum here which is worth visiting as it provides a lot of information about the Aletsch Glacier and how water was piped from here in wooden troughs and pipes to irrigate the farmland and pastures. The Massa Weg trail now follows the route taken by the wooden channels and is part of another walk I have described. (Hangebrucke, Belalp, Stausee Gibidum and the Massaweg)
Then, follow the path towards the Bettmerhorn. You will notice that the yellow signs are now blue and white. This indicates that you are leaving a good hiking trail and entering steep and rocky terrain. The path is well marked with blue and white flashes. (See the info below that I have provided re-grading of Swiss mountain trails and also what you can expect on the ascent of the Bettmerhorn. This is important as you are entering steep alpine terrain)
Make the ascent of the Bettmerhorn to the metal cross. There is a box with a summit book so you can add your name. Continue up and along the ridge to the summit. (4) Enjoy the views before turning around and returning to the Bergstation.
(3) From the Bergstation, follow head back towards Riederalp, the tracklog on the map shows that we took a slightly different way back following a piste before rejoining the Panorama Weg. There are many well-marked trails you could follow to get back to Reideralp. At Riederalp, there are cafes for refreshments and good facilities. Catch the cable car back down to your starting point.