You can save the particle info into a particle_output.dat file by checking “Save particles positions at end of run” in the Output pane. You can also set the velocity to zero if you want to (see below).
Then you can examine the file to make sure it is OK and rename it to particle_input.dat. To use this file as a starting point instead of the automatic Initial Condition, go to the solids>DEM (or Solids>CGP if you use CGP) and uncheck “Enable automatic particle generation”:
