If you are using the standard ILC Java toolchain, follow the WIRED event display instructions.
Otherwise, Geant4 can dump HepReps to a zip file.
/vis/scene/create /vis/scene/add/logicalVolume /vis/open HepRepXML /vis/viewer/set/culling global /vis/viewer/flush
JAS3 can open these files and will automatically startup WIRED4 with the loaded HepRep.
This environment variable should also be set so that invisible volumes are not included in the output file.
export G4HEPREPFILE_CULL=1