docs: Add user guide for change the stream description.

templates/zerver/help/change-stream-description.md

@@ -0,0 +1,25 @@
+# Change the stream description
+
+Note: Only administrators can change a stream's description.
+
+To change a stream's description, you'll first need to access
+your current stream subscriptions.
+You can do this by clicking on the settings cog at the top of
+your streams list on the left.
+
+![list of streams](/static/images/help/list-of-streams.png)
+
+(You can also access current stream subscriptions by clicking on
+**Manage Streams** from the settings cog (![](/static/images/help/cog.png))
+in the top right.)
+
+A window with your current stream subscriptions will appear.
+From the left, select the stream whose description you'd like
+to change.
+
+![change description field](/static/images/help/change-stream-description.png)
+
+Under **Administrator settings** on the right, there is a field
+with the current stream description.
+Change your stream's description in this field, and click
+**Change stream description** to save the change.

templates/zerver/help/index.md

@@ -89,7 +89,7 @@ as a “**realm**”.
 * [View messages from a stream](/help/viewing-messages-from-stream)
 * [The #announce stream](/help/announce-stream)
 * [Add or invite someone to a stream](/help/add-invite-stream)
-* Change the stream description
+* [Change the stream description](/help/change-stream-description)
 * [Rename a stream](/help/rename-stream)
 * Preview a stream (not implemented)
 * [Unsubscribe from a stream](/help/unsubscribe-stream)