To display particles outside the source in MCNP, utilize the "plot" command in the visual editor to visualize particle tracks toward the tally region. The "plot" command can also be applied in the MCNP output file for viewing particle paths in the tally area. Additionally, the "track" option in the input file allows for tracking particles through specified regions. This approach enables effective visualization of particle movement from the source to the tally region. Implementing these commands will enhance your understanding of particle behavior in MCNP simulations.