This is part of a beginner's learning guide for Maya. Tutorials in this series are short but cover a single topic in each one.
Enabling Raytacing For Maya Software
Open your render settings by going to window>rendering editors>render settings. Go to the Maya software tab.
Go down to raytracing quality and check raytracing.
Enabling Raytracing In Mental Ray
In Mental Ray, raytracing is enabled by default. If for some reason it's not enabled, open the render settings, go to the Mental Ray tab.
Under rendering features, go to secondary effects and check raytracing.