This is indeed a tricky one. It took me a while to get it to work and even still gives me fits but...

First and foremost, you have to turn off the car and wait. Maybe five to ten minutes. (This allows time for the oil to fall back down into the pan.) Turn the key to "on". Then press the button on the gauge display two times in a row. If you still only see the FSS display. Keep waiting. And keep pressing the button every so often. Eventually, you will see the oil can symbol and the status of your oil level.

Keep trying, you'll get it.