Fix sphinx-config.rst: a few words about enabling the autodoc extension

docs/source/sphinx-config.rst

@@ -21,7 +21,17 @@ Note that there exist numerous other nice themes out there, so if you're not par
 
 Autodoc configuration
 *********************
-Continuing, if we want Sphinx to autogenerate documentation from the comments of our code using the ``autodoc`` extension, we have to point Sphinx to the directory in which our Python source codes reside. This can be done by uncommenting and altering the following lines, which are generally found at the top of the file:
+Continuing, if we want Sphinx to autogenerate documentation from the comments of our code using the ``autodoc`` extension, we first have to enable it by adding its name to the ``extensions`` list:
+
+.. code-block:: python
+   :emphasize-lines: 4
+
+   # Add any Sphinx extension module names here, as strings. They can be
+   # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
+   # ones.
+   extensions = [ 'sphinx.ext.autodoc' ]
+
+Then its necessary to point Sphinx to the directory in which our Python source codes reside. This can be done by uncommenting and altering the following lines, which are generally found at the top of the file:
 
  .. code-block:: python
     :emphasize-lines: 3
@@ -53,4 +63,4 @@ Save and close the file (Ctrl+X -> Enter -> Y -> Enter).
 
 Apart from specifying the dependencies of our package, the ``requirements.txt`` file can be used to batch install any such dependencies by calling ``sudo pip install -r requirements.txt``. For more information on requirements files, you can have a look at `pip's documentation <https://pip.pypa.io/en/stable/user_guide/#requirements-files>`_. 
 
-We will later also use the ``requirements.txt`` file when configuring the building process of our ReadTheDocs documentation. If we didn't have the requirements file, then ReadTheDocs would fail to run ``autodoc`` in order to generate our documentation from the comments in our source code. In other words, when building our documentation, RTD calls a ``pip install -r requirements.txt``, which installs any requirements in a virtual environment, which is then where ``sphinx-apidoc`` is run.
+We will later also use the ``requirements.txt`` file when configuring the building process of our ReadTheDocs documentation. If we didn't have the requirements file, then ReadTheDocs would fail to run ``autodoc`` in order to generate our documentation from the comments in our source code. In other words, when building our documentation, RTD calls a ``pip install -r requirements.txt``, which installs any requirements in a virtual environment, which is then where ``sphinx-apidoc`` is run.