Review the MCNP Version 6.2 Release Technical Report for step-by-step instructions on the script-based installation process and system requirements. User's Manual Code Version 6.2 - MCNP
Under the U.S. Export Control Regulations (EAR), specifically the Nuclear Regulatory Commission (NRC) and Department of Energy (DOE), MCNP 6.2 is classified under Export Control Classification Number (ECCN) 3D201 or similar. This means: mcnp 62 download top
MCNP 6.2 is a masterpiece of computational physics. Treat it with the respect—and legal care—it deserves. By pursuing the legitimate "top" distribution channels, you protect your career, your institution, and the integrity of your science. Review the MCNP Version 6