With the elastic band you can secure your phone from sliding out. Stretch the elastic band as shown in the instructions over the V shaped cutouts. However, we recommend to hold your Google Cardboard in your hands, to secure your smartphone additionally.

Along with the head strap you received two Velcro tape stickers. Those have to be stuck to the outside left and right of your Cardboard. Ideally a bit higher than half.

The lenses should be already secured into position, however could have been shifted. The greater curvature has to face to the smartphone.