Via scripts... SetRTPCValue expects 3 arguments: RTPC name or ID, RTPC Value, and GameObjectID. If you leave GameObjectID default, it will set the RTPC globally. If you set GameObjectID to a specific object, it will only affect the RTPC for that game object. Via Wwise Authoring... Alternatively, you can create events in Wwise that set RTPC values. If you're using this method, pay close attention to the Event Action that sets the RTPC. It can be set to Global or Game Object under the scope column.
Hope this helps :)