Small documentation update to include how to _use_ InferenceObjective in the API summary

Author: kfswain

site-src/api-types/inferenceobjective.md

@@ -9,6 +9,10 @@
 
 The **InferenceObjective** API defines a set of serving objectives of the specific request it is associated with. This CRD currently houses only `Priority` but will be expanded to include fields such as SLO attainment.
 
+## Usage
+
+To associate a request to the InferencePool with a specific InferenceObjective, the system uses a specific header: `x-gateway-inference-objective` with the value of the header set to the InferenceObjective metadata name. So the calling client must set the header key/value on the request to associate the selected InferenceObjective. If no InferenceObjective is selected, default values are used.  
+
 ## Spec
 
-The full spec of the InferenceModel is defined [here](/reference/x-spec/#inferenceobjective).
+The full spec of the InferenceObjective is defined [here](/reference/x-spec/#inferenceobjective).