Clean the surface with a powerful all purpose cleaner like T.S.P (tribasic sodium phosphate) and let it dry. Create desired pattern using a pencil to mark the position of each tile. Use a ruler and a level as needed. Do not attempt to install tiles on a freshly painted wall. Allow a 3 weeks period for the paint to set and dry properly. Avoid touching the adhesive part with your fingers. To remove a tile, use a hair dryer to heat up the surface and gently remove tile starting with the corners.