Installing marble on walls can add elegance and sophistication to any space. Here's a general guide on how to install marble on walls:

1. Prepare the Surface: Ensure that the wall surface is clean, dry, and free of dust, grease, and debris. Repair any cracks or imperfections in the wall surface and allow them to dry completely.

2. Plan the Layout: Determine the layout of the marble tiles on the wall, taking into account any patterns or designs. Use a level and chalk lines to mark the starting point and ensure that the tiles are installed evenly.

3. Prepare the Marble Tiles: Measure and cut the marble tiles as needed to fit the wall layout. Use a wet saw or tile cutter to make precise cuts, and wear appropriate safety gear, such as goggles and gloves, during this process.

4. Mix Thin-Set Mortar: Prepare thin-set mortar according to the manufacturer's instructions. Mix it to a thick, creamy consistency using a mixing paddle and bucket.

5. Apply Thin-Set Mortar: Using a notched trowel, apply a layer of thin-set mortar to a small section of the wall. Hold the trowel at a 45-degree angle and comb the mortar in one direction to create grooves for better adhesion.

6. Install Marble Tiles: Press the marble tiles firmly into the thin-set mortar, starting at the bottom of the wall and working your way up. Insert tile spacers between the tiles to maintain uniform spacing and alignment.

7. Check for Level and Alignment: Use a level to ensure that the tiles are straight and level as you install them. Adjust the position of the tiles as necessary to maintain proper alignment and spacing.

8. Grout the Joints: Once the thin-set mortar has cured (usually 24-48 hours), remove the tile spacers. Prepare grout according to the manufacturer's instructions and apply it to the joints between the tiles using a grout float. Work the grout into the joints at a 45-degree angle, making sure to fill them completely.

9. Clean Excess Grout: After applying the grout, wait 10-15 minutes for it to set slightly, then use a damp sponge to wipe away excess grout from the surface of the tiles. Rinse the sponge frequently and change the water as needed to avoid smearing grout over the tiles.

10. Seal the Tiles (Optional): Consider applying a penetrating sealer to the marble tiles to protect them from stains and moisture. Follow the manufacturer's instructions for application and drying time.

11. **Final Touches**: After the grout has fully cured (usually 24-72 hours), buff the tiles with a soft cloth to remove any haze or residue. Reinstall any fixtures or trim pieces that were removed during the installation process.

By following these steps and using proper techniques, you can install marble tiles on walls and create a stunning, durable surface that enhances the beauty of any room. If you're unsure about any aspect of the installation process, consider consulting with a professional tile installer for guidance.