Carefully peel off the backing paper from the wall sticker, starting from one corner. Avoid touching the adhesive side to prevent any fingerprints or dirt. Slowly apply the sticker to the wall, starting from the top or one corner, and smooth it out with a squeegee or a soft cloth as you go. Work your way down, ensuring there are no air bubbles trapped underneath the sticker. If you encounter any bubbles, gently lift the sticker and smooth them out.