Make sure wall surface is clean and dry. If you want, use a level, ruler, and pencil to mark out where your words should go.
Starting at one edge, peel chalkboard away from its backing.
Gently press chalkboard calendar to wall, so it stays in place.
Starting from a corner and working outward, firmly smooth calendar onto wall. A squeegee is useful for this if you have one. If you get a stubborn air bubble that won't come out, peel part of poster away from wall and re-stick or prick the side of the bubble with a pin and gently coax air out.