diff --git a/exercice_4/README.md b/exercice_4/README.md
index 6cc11c0..a90350a 100644
--- a/exercice_4/README.md
+++ b/exercice_4/README.md
@@ -1,41 +1,52 @@
 # Readme exercice 4
 
 code by Marti Bosch (marti.bosch@epfl.ch) and Marc Schwaerzel (marc.schwaerzel@epfl.ch) 
 
 ## Exercise 1
 
 ## Exercise 2
 2.2 We used shared pointers for the pybind of the classes compute and compute_temperature in order not to desallocate when python's reference count goes to 0. A unique pointer could lead to a segmentation fault (memory allocation issues).
 2.3 We used the method where we put setters directely in the compute_temperature.py in order to access private members from outside the class.But there is a smarter way to access private members --> reread class notes and implement them.
 
 ## Exercise 3
 created bind for csvwriter, evol.setNsteps, evol.setDumpFreq and evol.evolve...
 
-still need something for     self.system_evolution.addCompute(compute_temp) ln50 of main
 
 
 ## Instructions to run the code
 
 To run the code follow the instructions:
 
 1) Create a new directory in the exercice_4 directory and go into that folder:
 	
 	$ mkdir build
 	$ cd build
 
 2) Check whether your paths are set correctly
 
 	$ ccmake ../
 
 2) Compile the code:
 	
 	$ cmake ../
 	$ make
 
-3) Then run as follows
+3) Find an input file and move it into our current build file:
+	e.g. take the input file created with generate_heat_distribution.py from exercice_3 
+	(see README from exercice_3 to use the python function)
 
-	$ ./particles --help
+4) Make a folder to store the ouputs files
+	$ mkdir dumps
+ 
+5) Then run as follows
+
+	$ python ./src/main.py arg1 arg2 arg3 arg4 arg5
     
-    Usage: ./particles nsteps dump_freq input.csv particle_type timestep
-	    particle type can be: planet, ping_pong, material_point
+    where: 	arg1 is the number of steps (e.g. 1000)
+	   	arg2 is the dump frequency (e.g. 10)
+	   	arg3 is the input filename (e.g. step-00000.csv from last ex)
+	   	arg4 is the particle type (e.g. material_point)
+	        arg5 is the timestep (e.g. 1)
+
+