To display particles outside the source in MCNP, you can use the "plot" command in the MCNP visual editor. This will allow you to plot the particle tracks from the source to the tally region. You can also use the "plot" command in the MCNP output file to view the particle tracks in the tally region. Additionally, you can use the "track" option in the MCNP input file to specify specific regions to track particles through. This will allow you to see the paths of particles from the source to the tally region. I hope this helps guide you in visualizing particles outside the source in MCNP.