How can i change the Top Component to Bottom Side In (Allegro PCB Editor)?

Hi..

     I was using the Allegro PCB Editor(OrCAD 16.0). In that all components are in same side.So only i had asked that doubt to change the component top to bottom.

   This Option is been not enabled in my Edit -> Move and then click the RMB and mirror the component.

  What is RMB ?

Send the details clearly.