Join our CAD community forums where over 25,000 users interact to solve day to day problems and share ideas. We encourage you to visit, invite you to participate and look forward to your input and opinions. Acrobat 3D, AutoCAD, Catia, Inventor, IronCAD, Creo, Pro/ENGINEER, Solid Edge, SolidWorks, and others.
First create an assembly and the make sure that gears are properly engaged and constrained. Using move or rotate command in the mates tool bar set for options for physical Dynamics. Grab one gear and it will drive the others also.
Or use simulation tool under insert menu and add motor to one of the gears and it will drive the others.
Hope this is helpful.