Update install instructions

INSTALL.md

@@ -43,3 +43,42 @@ Uninstalling
 ```
 $ pip uninstall msspec_dfm
 ```
+
+
+
+Running the code
+================
+
+The program can be run either from the command line or from a Python script.
+
+Command-line
+------------
+
+The executable is called 'eps'. Type in 'man eps' to get more help. It has 3 main sub-commands:
+
+- generate
+- compute
+- plot
+
+Begin by generating an input file with default values:
+
+```
+$ eps generate
+```
+
+Then, edit this input file according to your needs and compute
+
+```
+$ eps compute Data/epsilon.dat
+```
+
+Finally you can plot the results
+
+```
+$ eps plot diel_func
+```
+
+Python bindings
+---------------
+
+Have a look to [this example](./examples/example00.py)