Hello there and welcome to the Wowza support forum.
You will need to create a .stream file that points to the orgin stream, start it in the stream manager or StartupStreams.xml then you can use the push publishing module to send it out. Those are the basic steps.
So you would have on the edge /content/origin.stream
Edge: StreamManger start origin.stream on edge application with MediaCaster type "liverepeater"
PushPublish module installed on edge pushes origin.stream