As YouTube Vanced is no longer available, you have to download it from third-party websites, which is dangerous. Begin by looking for a trusted website providing the current APK of YouTube Vanced. Be sure to check the source so that you do not download malware files. In case you need to log in to your Google account, you will also have to download MicroG. As a precaution before installing, enable "Install from Unknown Sources" on your phone settings. After you install it, launch YouTube Vanced and tweak settings such as ad-blocking, background playback, and dark mode. Because Vanced is no longer maintained, you may have problems in the long run. For a better experience, look into ReVanced or YouTube Premium.