1. Backup Your Chats: Before installing GB WhatsApp APK, it's advisable to backup your existing WhatsApp chats and media files. You can do this by going to WhatsApp settings > Chats > Chat backup and tapping on "Back Up" to create a backup on your device or cloud storage.

2. Download GB WhatsApp APK: GB WhatsApp is not available on the Google Play Store, so you'll need to download the APK file from a trusted source. Search online for "GB WhatsApp APK" and choose a reliable website to download the latest version of the APK file.

3. Enable Unknown Sources: By default, Android devices do not allow installation of apps from unknown sources. To enable it, go to your device's Settings, then navigate to Security or Privacy settings. Look for the option called "Unknown Sources" or "Install apps from unknown sources" and enable it by toggling the switch.

4. Install GB WhatsApp: Locate the downloaded GB WhatsApp APK file on your device (usually in the Downloads folder) and tap on it to initiate the installation process. Follow the on-screen instructions to install the app.

5. Verify Your Number: Once GB WhatsApp is installed, launch the app. It will prompt you to enter your phone number. Enter the phone number you want to use with GB WhatsApp and wait for the verification process to complete. You will receive a verification code via SMS or a phone call.

6. Restore Chats: After verifying your phone number, GB WhatsApp will give you an option to restore your chats from the backup you created in Step 1. If you want to restore your chats, tap on the "Restore" button and wait for the process to finish. This will bring back your previous WhatsApp conversations and media files.

7. Set Up Your Account: Follow the on-screen instructions to set up your GB WhatsApp account. You can customize your profile, privacy settings, themes, and other preferences according to your liking. Explore the app's settings to take advantage of the additional features and customization options offered by GB WhatsApp.

Remember that GB WhatsApp is a third-party app and not endorsed by WhatsApp or Facebook. Be cautious while using modified versions of WhatsApp, as there may be security risks associated with unofficial apps.