If you are going to stick stickers you need the following:

• dust-free cloth
• cleaning agent
• degreaser
• painting tape
• measuring tape
• spatula or bank card
• pin

The sticker must consist of one part.
The substrate does not have to be completely flat for this method.

• Stick the sticker on the left and right with masking tape.
• Determine the exact position using the measuring tape.
• Is the sticker in the right place? Paste in the middle of the sticker from top to bottom
  below a strip of painting tape.
• Now release one of the sides and fold it to the other side.
• Remove the backing sheet until just before the painting tape.
• Cut or cut the back sheet.
• Rub the sticker firmly from the center with a spatula or bank card.
• Then loosen the painting tape on the other side.
• Remove the painting tape in the middle.
• Flip the other side and remove the remainder from the backing sheet.
• Now attach the other side in the same way as above.
• Any air bubbles can be removed by poking with a pin in the middle
  and rub away from the outside to the hole.