You don't need to use StreamManager. An RTMP live encoder publishes directly, i.e. pushes a stream to Wowza. StreamManager is used to start MediaCaster streams such as IP cameras or mpeg-ts encoders that have a rtsp or udp urls that Wowza pulls a stream from
So when you start your RTMP live encoder and publish a stream to a Wowza application you will see a publish event in the logs, and you will be able to play the stream back in a playback client right away.