V-Ray is a renderer plugin for Maya. In order to use V-Ray, you must first enable it in the Plug-in Manager. You can do that by going to Window > Settings/Parameters > Plug-in Manager menu and clicking the Loaded check box to load it manually. If you want V-Ray to be automatically loaded every time Maya starts you should check the Auto Load box.
In order to use V-Ray, you must first select it as your current renderer. You can do that by choosing V-Ray from the Render Using drop down menu in the Render Settings dialog.
In Maya, the V-Ray parameters are divided into several tabs in the render settings dialog; additionally each tab is divided into several rollouts:
For a more detailed description of each layout, check out the sections below:
VRay
Settings