Changing the wallpaper on WhatsApp is a straightforward process. Here are the steps to do it:

For iOS:

1. Open WhatsApp: Launch the WhatsApp application on your iPhone.
2. Go to Settings: Tap on the "Settings" icon located at the bottom right corner.
3. Chats: Select "Chats" from the Settings menu.
4. Chat Wallpaper: Tap on "Chat Wallpaper."
5. Choose Wallpaper: You will have several options:
   • Wallpaper Library: Select from WhatsApp's built-in wallpapers.
   • Solid Colors: Choose from a variety of solid colors.
   • Photos: Select a photo from your own gallery.
6. Set Wallpaper: Once you've selected your desired wallpaper, adjust it as needed and tap "Set."

For Android:

1. Open WhatsApp: Launch the WhatsApp application on your Android device.
2. Open a Chat: Go to any individual or group chat.
3. Menu Options: Tap the three vertical dots in the upper right corner to open the menu.
4. Wallpaper: Select "Wallpaper" from the menu.
5. Choose Wallpaper: You will have several options:
   • My Photos: Choose a photo from your gallery.
   • Default Wallpaper: Revert to the default wallpaper.
   • Wallpaper Library: Select from WhatsApp’s built-in wallpapers.
   • Solid Colors: Choose from a variety of solid colors.
6. Set Wallpaper: After selecting your wallpaper, you can preview it. Tap "Set Wallpaper" to apply it.

Notes:

• Changing the wallpaper in WhatsApp will affect the background for all chats, not just a specific one.
• Ensure you have the latest version of WhatsApp for the best experience and access to all features.