factoring out some text that's shared between guides

docs/tutorials/add_packages.txt

@@ -0,0 +1,29 @@
+The **User Environment** is a conda environment that is shared by all users
+in the JupyterHub. Libraries installed in this environment are immediately
+available to all users. Admin users can install packages in this environment
+with ``sudo -E``.
+
+#. Log in as an admin user and open a Terminal in your Jupyter Notebook.
+
+   .. image:: ../images/notebook/new-terminal-button.png
+      :alt: New Terminal button under New menu
+
+#. Install `gdal <https://anaconda.org/conda-forge/gdal>`_ from `conda-forge <https://conda-forge.org/>`_.
+
+   .. code-block:: bash
+
+      sudo -E conda install -c conda-forge gdal
+
+   The ``sudo -E`` is very important!
+
+#. Install ``there`` with ``pip``
+
+   .. code-block:: bash
+
+      sudo -E pip install there
+
+The packages ``gdal`` and ``there`` are now available to all users in JupyterHub.
+If a user already had a python notebook running, they have to restart their notebook's
+kernel to make the new libraries available.
+
+See :ref:`user_environment` for more information.