update README

FCCee/FullSim/ALLEGRO/ALLEGRO_o1_v03/README.md

@@ -7,6 +7,18 @@ If you need to modify the geometry, follow instructions [here](https://fcc-ee-de
 source /cvmfs/sw-nightlies.hsf.org/key4hep/setup.sh
 ```
 
+
+## Running the simulation
+You can produce a file containing the Geant4 simulated hits in the detector with:
+```
+ddsim --enableGun --gun.distribution uniform --gun.energy "10*GeV" --gun.particle e- --numberOfEvents 100 --outputFile ALLEGRO_sim.root --random.enableEventSeed --random.seed 42 --compactFile $K4GEO/FCCee/ALLEGRO/compact/ALLEGRO_o1_v03/ALLEGRO_o1_v03.xml 
+```
+
+You can also retrieve a simulation file already produced from here: `https://fccsw.web.cern.ch/fccsw/filesForSimDigiReco/ALLEGRO/ALLEGRO_o1_v03/forTests/pythia_ee_z_qq_10evt_ALLEGRO_sim.root`
+
+
+## Running the digitization and reconstruction
+
 Retrieve the files needed later for digitization/reconstruction (e.g. noise values, machine learning models for calibration, ...)
 NB: if you do not have direct access to eos, you can retrieve those files from here: `https://fccsw.web.cern.ch/fccsw/filesForSimDigiReco/ALLEGRO/`
 ```
@@ -17,18 +29,18 @@ or
 scp <user>@lxplus.cern.ch:/eos/project/f/fccsw-web/www/filesForSimDigiReco/ALLEGRO/ALLEGRO_o1_v03/* .
 ```
 
-## Running the simulation
-```
-ddsim --enableGun --gun.distribution uniform --gun.energy "10*GeV" --gun.particle e- --numberOfEvents 100 --outputFile ALLEGRO_sim.root --random.enableEventSeed --random.seed 42 --compactFile $K4GEO/FCCee/ALLEGRO/compact/ALLEGRO_o1_v03/ALLEGRO_o1_v03.xml 
-```
-
-## Running the digitization and reconstruction
+Run the reconstruction with:
 ```
 k4run run_digi_reco.py
 # you can then print the rootfile content with
 podio-dump ALLEGRO_sim_digi_reco.root  
 ```
 
+This will run by default on the `ALLEGRO_sim.root` file. To run on a different file (e.g. `pythia_ee_z_qq_10evt_ALLEGRO_sim.root`) use:
+```
+k4run run_digi_reco.py --IOSvc.Input <inputfile>
+```
+
 ## Dirac submission
 The following is not yet ready, we have to implement ddsim as a generator in diract to do particle gun transformation
 You need to create a tarball containing the files needed for reconstruction and upload it at the right place with dirac commands