[totem/mallard-documentation] Clarify where to set loading subtitles automatically

[Andre Klapper <aklapper src gnome org>]

commit d78dda5c34ab93291811514929fd03bc73ba50ac
Author: Andre Klapper <a9016009 gmx de>
Date:   Fri Jan 11 19:02:23 2019 +0100

    Clarify where to set loading subtitles automatically

 help/C/subtitles.page | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/help/C/subtitles.page b/help/C/subtitles.page
index bd2f3243..c20266f2 100644
--- a/help/C/subtitles.page
+++ b/help/C/subtitles.page
@@ -23,10 +23,11 @@
   <title>Subtitles</title>
 
   <p>
-  <app>Videos</app> usually loads subtitles automatically. If it does not, view
-  them in the following way:
-  </p>
+  <app>Videos</app> loads subtitles automatically if <gui>Load subtitle files
+  when movie is loaded</gui> is enabled in the 
+  <link xref="preferences">Preferences</link>.</p>
 
+  <p>To manually load a file with subtitles for a movie:</p>
   <steps>
     <item>
       <p>Press the menu button in the top-right corner of the window and select