First you stick the windowsill together and then under the window. As soon as the glue is dry, you can paint the part with acrylic paints or other wooden colors. It is best to stick the floor with an adhesive stick so that the paper does not roll. Pay attention to it: the base holes are on the back of the floor.
Next you stick the shelf floors (and lid) together. When plugging in the shelves, everything is right together if there is no surge of the "boards". If it stands as in the picture, turn the shelf so that it is no longer over. Finally, stick the bottom and lid.
Now you can glue the shelves directly on the side parts and then paint. Put the box together when you are unsure about positioning the shelves.
You will probably not see wallpaper, but if you want, you can also stick the side parts beforehand.
The easiest way to decorate the shelves now and then put the box together. If you want to distribute LED on the shelves, you can also drill holes and lay the cables better in the dismantled state.
An advanced video is currently in progress and will soon be linked here.