To render from the command-line you can use the CommandLine tool located in you Cinema 4D application installation folder. Alternatively the Cinema 4D application itself can also be used.
Where <device_id> is the GPU device id you wish to render with.
To render a scene located at c:\path\to\scene.c4d on using only GPU device 1 only use:
Same To render the same scene rendered using both GPU device 0 and 1:
The CommandLine tool supports multiple parameters for customizing rendering (frame ranges, image output options etc.) For more details please consult the "Cinema 4D and the Command Line" section of the Cinema 4D documentation.