updating action command instructions in doc

Author: TyDunn

docs/core/actions.rst

@@ -84,8 +84,16 @@ The only thing your action server needs to install is ``rasa-sdk``:
     create a separate container for your action server. In this
     separate container, you only need to install ``rasa-sdk``.
 
-If your actions are defined in a file
-called ``actions.py``, run this command:
+If you have ``rasa`` installed, run this command to start your action server:
+
+.. code-block:: bash
+
+    rasa run actions
+
+.. _custom_action_example:
+
+Otherwise, if your actions are defined in a file
+called ``actions.py`` and you do not have ``rasa`` installed, run this command:
 
 .. code-block:: bash