The next thing you want to do is flip the insert over and completely remove the two pieces marked in picture 2. Afterwards they should look like in picture 3.
The next thing you want to do is extend the area that will hold the card. So flip the insert over again and scratch/cut a straight line next to both sides of this area. Don’t cut through the cardboard, it should just be deep enough to make the bending easier. The cut should be 2cm (0.787401575 inches) away from the edge of the box (see images 4 and 5).
Now cut through the cardboard at the four edges displayed in image 6 and bend the inner sides up (also displayed in image 6).
Now fold the insert and bend the inner sides down as displayed in image 7.
Now flip the insert over and put some transparent sticky tape around the edges marked on image 8.
Finally, put your game into the insert as displayed on image 9. If you did everything right it should fit perfectly.