1. First, you need to download and install apktool on your computer. This is an APK decompilation tool that can be used to decompress and modify APK files.
2. Copy the Douyin APK file to your computer, use apktool to open the APK file, and decompress it.
3. Open the unzipped folder, find the AndroidManifest.xml file and open it with a text editor.
4. In the AndroidManifest.xml file, find the package attribute, modify it to the desired new package name, and save the modified file.
5. Use apktool to repackage the modified folder and generate a new APK file.
6. Finally, you need to use a signing tool to sign the new APK file to ensure that it can be installed and run normally on the phone.