Thoroughly vacuum the area and give the wall a once over with a damp sponge or cleaning cloth.
Tile adhesive painted walls.
For large tiles only a flexible tile adhesive like webercol flex should be used.
Seal the walls with a skim coat and let it dry thoroughly.
You can leave the paint on drywall provided there are not several coats and the tile epoxy will adhere with no problem.
Mix and apply the selected tile adhesive with a suitable notched trowel.
If the substrate is non porous porcelain tiles etc priming is highly recommended with webercol prime.
Things you will need orbital sander 80 120 grit sandpaper safety glasses dust mask rags tape measure pencil 48 inch spirit level mastic or thin set mortar grooved trowel tile spacers tile cutting tool grout grout spreader sponge grout haze remover optional distilled white vinegar optional.
If the walls you want to tile are concrete walls with paint on them remove the paint before you install tile so the tile adhesive has something to grab onto and hold the tile in the correct place.
Acrylpro professional ceramic tile adhesive is a professional acrylpro professional ceramic tile adhesive is a professional formula adhesive with high bond strengths.