DOCS-7836 clarify --host for connecting to secondaries

Author: Isabella Siu

source/includes/options-shared.yaml

@@ -77,10 +77,17 @@ description: |
 
   .. code-block:: none
 
-     <replSetName>/<hostname1><:port>,<hostname2><:port>,<...>
+     --host <replSetName>/<hostname1><:port>,<hostname2><:port>,<...>
 
-  You can always connect directly to a single MongoDB instance by
-  specifying the host and port number directly.
+  When specifying the replica set list format, {{program}} always connects to
+  the :term:`primary <Primary>`. 
+  
+  You can also connect to any single member of the replica set by specifying
+  the host and port of only that member:
+
+  .. code-block:: none
+
+     --host <hostname1><:port>
 
   .. versionchanged:: 3.0.0
      If you use IPv6 and use the ``<address>:<port>`` format, you must