The route starts on the bridge from the visitor center to the fields across the river. It then follows the standard hiking route up Ben Nevis to the top. It's an out and back route with the finish being at the same bridge.
Start from the bridge at the visitor center leads you through easy gravel paths on a slight incline for the first mile. Then the path turns to stone, but mostly flat and laid out for hiking. This is a popular hiking route and often quite crowded. After mile 3 at the main bend on the hike, gravel path resumes and gradually becomes more technical as you near the summit. In the last half mile, snow is a very real possibility year round. And visibility can be affected by cloud cover and mist. The final stretch will be either on rough rock path or snow. The path is clearly marked and easy to follow. This is an up and down route.
There is a stream half way up that could serve as an aid station for water. Though would recommend filters or planning to pack all your needs from the TH start.
Access to the TH is easy with parking at the visitor center. This is located a few minutes outside of the town of Ft William. Follow directions to Glen Nevis to park at the Ben Nevis visitor center. Cross river and turn right to join the Ben Nevis Mountain Path (left and clearly indicated). You'll have to clear a few sheep gates.