Update User_guide.rst

add `execute various scenarios`

doc/source/User_guide.rst

@@ -437,6 +437,10 @@ The input files required for each parameter, and their corresponding dimensions
   * `inf` refers to Infinity, indicating that there is no upper bound.
   * `None` refers to a null value for current item.
 
+Execute various scenarios
+-------------------------
+By employing command-line parameters, you can execute different scenarios using the model. For example, if you wish to run a scenario referred to as "low demand," you can prepare input data named `demand_low.xlsx`. Subsequently, when running the model, you can utilize command-line parameters to specify the scenario value. For instance, you can execute the model by executing the command `python run.py --demand=low`. 
+
 Tuning Model Parameters
 -----------------------