It sounds like you have developed an HTTP Provider of which you have configured and runs properly. If that is all you have created, there is no need to put anything in your Application.xml. However, if you have created an additional application module extending ModuleBase, then you would define this towards the end of the <Modules> section within the respective application's configuration (i.e. conf/[app-name]/Application.xml) as follows:
Then simply add that jar file to your lib/ folder and restart Wowza.
... [other modules] ...