The Dune7 is 10 minutes drive from Walvis Bay on paved roads. There is a guarded parking lot in front of the dune and a snack bar nearby. It's best to walk barefoot if the sand is not too hot.
There is an entrance fee, more for tourists than for locals. If you want to drive straight to the dune you pay extra. But it's worth it: the climb is fun (3 steps forward, 1-2 back) and at the top you have a magnificent view over the dunes. You go down with 7-mile boots.