You can't check it easily. There is no dipstick. Just like the automatic transmissions they've used on the ALH engine before North America got the PD with Tiptronic transmission, it is "sealed for life".
There is a cap over the fill plug, and you can only check the level by removing a plug in the drain, with the fluid at less than 30C (you'll need a computer interface to determine that), then raise the temperature to between 35 and 45 C. If fluid does not drip out when it gets up to temperature, then it needs fluid. If it does drip out, then it doesn't.
So if you're not experiencing problems, leave it alone.