The basic idea is to find the final while being given only your distance to it. To get the current distance, you can ask the Reverse Cache Box in your inventory, but it won't tell you the direction - that's for you to figure out! There's no limit to how many times you can ask, but try to keep your number of guesses as low as possible. Theoretically, you should only need 3 queries to triangulate on the cache, but in practice you'll probably need more. All instructions and necessary information needed to complete the cartridge are provided in the cartridge itself, which is multilingual.
The Reverse Wherigo is a generic cartridge that works on many such caches worldwide. To identify the Springfield East version, you must type this code into your player when asked:
703347
195793
845003
Once you zero in on a spot close to the final, you can try to find it yourself without any more queries. If you make a query within a very short distance, you'll receive the actual coordinates and can follow your GPS from there. Otherwise, you probably won't need your GPS receiver at all when playing this wherigo. After you make the find, feel free to post the stats (number of queries, etc.) from your search as part of your log. There's no "completion code" for this cartridge.
If you want to create your own Reverse Wherigo, you can do so using the passcode you receive at the end of the game. The passcode is unique to you and can't be shared with other cachers. Simply choose "create" rather than "play" when starting the Reverse Wherigo and enter your passcode at that point. You will need to be at the final location for your hide, with a good signal on your device. The cartridge will then give you the exact coordinates (which you'll need when creating the geocache online) and the three six-digit sequences that identify that location in the cartridge. Write these down, hide your container and create your very own Reverse Wherigo! Just be sure to notify -Waldmeister- as a courtesy (no advance permission needed).