In this case, Firstly you have to research about MC codes which is most suitable for your research fileld.
There is several MC codes that you can use efficiently. MCNP, Geant4 and Fluka are some of the well-known codes. On the other hand, they have different using procedures. Geant4 is quite strong code on high energy applications since MNCP and FLUKA are most user friendly codes and very powerfull in wide energy range. If you decide your code very well, then it will be more useful to investigate about user guides.