Just to make sure to there is no misunderstanding: you do not need to install Geant4.
If you are using a precompiled binary distribution (recommended), use bin/thisroot.sh.
If you have built ROOT from source, use the bin/thisroot.sh script in the install directory.
Thanks a lot for your reply and help until my problem has been solved!and you are my enlightenment teacher in Garfield++. that’s my result imported from the Ansys, I will try to solve how to show the three dimensional model and the 2D figure.