On the server running your Wowza Streaming Engine Manager UI, open the
[wowza-install]/manager/bin/startmgr.sh file if it's a Linux based OS, or
[wowza-install]/manager/bin/startmgr.bat on a Windows machine.
In the code caprt where the Java configuration parameters are set, you will find this parameter:
--httpPort=8088. You can change the port 8088 with a different port number. Please make sure that the new port you are using is not already being used by a different service that is running on your machine.
You will need to restart the Wowza Streaming Engine Manager service in order for the changes to be applied.