You're searching for a regular sized box on Walderton Down. Recommended parking is at CP1 below, which is just over a mile from the cache, although there are other odd spots in Walderton Village where you might be able to park a bit closer. Once you've done the cache do yourself a favour and walk on up the hill where you'll get fine views over Chichester Harbour, the Solent & Isle of Wight to the south; and North towards Uppark House & the South Downs. If you continue on this path through the woods there are other spectacular views to be had, and you could also visit Kingley Vale which is one of the finest and most ancient Yew Forests in Europe.
This cache is on the Western Downs Cycle Route, so if you've got a mountain bike, get it out & get peddling....