Changing from oil-based paint to latex paint on walls requires careful preparation to ensure a successful transition. Here are the key steps you should follow:

1. **Assessment:** Determine if the current oil-based paint is in good condition. If it is peeling or flaking, you will need to scrape, sand and repair the areas before applying the latex paint.

2. **Gather Supplies:** You will need liquid deglosser, sandpaper, painter’s tape, drop cloths, primer, latex paint, paint roller, paintbrushes, and a paint tray.

3. **Cleaning:** Clean the walls thoroughly with a mild detergent to remove any dirt or dust. Allow the walls to dry completely before proceeding.

4. **Deglossing:** Apply a liquid deglosser to the walls to remove the glossy finish of the oil-based paint. This step is optional but helps the new paint adhere better to the surface.

5. **Sanding:** Lightly sand the walls to roughen up the surface and promote adhesion. Wipe down the walls with a damp cloth to remove any sanding dust.

6. **Priming:** Apply a high-quality bonding primer that is specifically designed to cover oil-based paint. This will create a suitable surface for the latex paint to adhere to. Good option is Zinsser Cover Stain.

7. **Painting:** Once the primer has dried according to the manufacturer’s instructions, you can paint the walls with latex paint. Follow the proper technique and apply multiple thin coats for a smooth and even finish.

8. **Drying:** Allow the latex paint to dry thoroughly between coats. Follow the recommended drying times on the paint can to prevent any issues with drying and finish quality.

By following these steps carefully, you can successfully change walls from oil-based paint to latex paint with a professional-looking finish.