While the Dolphin emulator can often run .nkit files directly, they are sometimes prone to bugs or crashes. Many users prefer to use the NKit processing app to convert them back to a standard .iso or .rvz format for better performance.
It looks like you're searching for a specific file download for (USA version, multi-language) in the .nkit format. Download WWE '12 (USA) (En,Fr,Es).nkit
Are you planning to run this on or through an emulator ? While the Dolphin emulator can often run