You eat it by opening your mouth slightly wider than you would for a regular Oreo. Perhaps a quarter of an inch more. If that's a problem, you might be in a TMJ crisis.
As for the cookie? It's an Oreo. A little bigger. A little crunchier. Slightly more chocolatey. It does not kill people upon ingestion, nor does it shatter jawbones.
The trick is to eat half as many Triple Double Oreos as you would regular Oreos. It's not hard. Really.