You should have the manager app installed if you flashed it from the Magisk repo. Also, this is a legacy profile by the ARISE team that sounds amazing on any headphones I've used. Just unzip it to the root of your storage, and select the profile from within Viper by long-pressing on the headset tab. Also, if you use streaming services like Spotify, you'll also want to install the audio compatibility patch from Magisk. When it asks, don't skip the first patch, and then apply it with the new logic. It'll also ask if you want to perform a workaround, which is only necessary for some phones. If you have problems, reinstall it and use the workaround.