I can view the Resource graph as well as resource usage graph by clicking
the Resource tab from PWA.
I know that these views are defaults views when you intsall Project Server!!
In PWA, navigate to the Resource Center. Select one or more (up to 30)
resources and click on the "Availability" link. This will give you 4
availability views to choose from, with a grid below the graph that
shows you the data being used to construct the graph.