you can do it in a simple way
If you have added your IHS to websphere admin console .. then all you need to do is to map your application to the cluster+IHS server.
Once that is done.. generate and propagate the plugin.
If you like to know how it works.. open the plugin-cfg.xml file and see how the websphere application server cluster is defined in it. There will be a tag and inside that you can see the clones/JVMs of the cluster defined.