DOCSP-48252: autocomplete index link/note (#586)

* DOCSP-48252: autocomplete index link/note

* SA small fix

(cherry picked from commit 5eb8fc6)

Author: rustagir

Diff for: source/fundamentals/atlas-search.txt

@@ -93,18 +93,24 @@ Autocomplete
 Use the ``Autocomplete()`` method to search for a word or phrase that contains a
 sequence of characters from an incomplete input string.
 
-The following example performs an autocomplete search on the ``guitars``
-collection using the string "Gib" in the ``make`` field.
+The following example performs an autocomplete query on the ``make``
+field for text that starts with the string ``"Gib"``.
 
 .. literalinclude:: /includes/fundamentals/code-examples/atlas-search/AtlasSearchExamples.cs
    :start-after: // start-autocomplete-search
    :end-before: // end-autocomplete-search
    :language: csharp
    :dedent:
 
-.. note::
+.. note:: Index for Autocomplete Queries
 
-   If the field you are searching on is indexed by a search index, you must pass the index name to the ``Autocomplete`` call. If a search index does not exist, the default index is used.
+   You must create an Atlas Search index that supports autocompletion
+   to successfully perform autocomplete queries. To learn more, see
+   :atlas:`How to Index Fields for Autocompletion </atlas-search/field-types/autocomplete-type/>`
+   in the Atlas documentation.
+
+   After you create the Atlas Search index, you must pass the index name to
+   the ``Autocomplete()`` method, as shown in the preceding code.
 
 The search returns the following document: