GMediaServer is run from the command line. It supports the usual --help option which displays usage and option information. GMediaServer expects one or more directory arguments, specifying where audio files are stored. You should probably also use the -i (--interface) option to specify which interface GMediaServer should listen on. The first times you run GMediaServer it would also be a good idea to increase the verbosity. Example:
./gmediaserver -ieth1 -v4 /audio
Check out the --profile option, which allows settings for certain devices to be automaticly enabled.