If you didn't get an owners manual with the car you can find it in related links.
According to page 1-6 it says the large lever on the side of the seat closest to the front of the seat will raise and lower it.
On page 9-49 it says The tethered fuel cap is behind the fuel door on the vehicle's passenger side. To open the fuel door, push the rearward center edge in and release. When applied pressure is removed, the fuel door will spring partially open.
This is a brand new vehicle that came with an owners manual. Open that manual and read. There you will find the answer to this question.
Push flap and springs open
there is not one. you push in the left side of it and it will spring open
It should be like the Chevrolet Volt's release button which is somewhere on the driver side door typically hidden somewhere on the controls module.
Check the sticker in the door jam or consult the drivers manual.
The Door - 2013 II was released on: USA: 19 March 2013
The Other Door - 2013 was released on: USA: 29 March 2013 (internet)
You push the gas door in and it releases.
Door to Door - 2013 The Costume Party 1-0 was released on: USA: 20 December 2013
Trouble Next Door - 2013 was released on: USA: 7 January 2013
The One Way Door - 2013 was released on: USA: 5 December 2013
The Door - 2013 I was released on: Poland: 5 January 2013 (limited) USA: 11 February 2013 (internet)
There is no release; just push one side of the fuel door and it pops open.