Hi,
Take a look at WMSProperties in the Server API docs.
You can add or modify a property by using getProperties().setProperty(name, value); There is a getProperties() method for most high level objects in Wowza.
To access your property, use one of the getProperty*(name, defaultValue); methods. If the value is not a simple object then you will need to type cast the call. e.g.
MyObject myObject = new MyObject();
appInstance.getProperties().setProperty("myObject", myObject);
. . .
MyObject myObject = (MyObject) appInstance.getProperties().get("myObject");
. . .
WMSProperties extends Map so you can use any Map as well.
Roger.