precise that logic for schedule is in index.md

Author: fmichonneau

_extras/customization.md

@@ -175,10 +175,10 @@ workshop you will be teaching  (`dc`, `lc`, or `swc`).
 
 If you wish to create your own custom schedule, an empty template is available in
 `_includes/custom-schedule.html`. In this file, we provide the structure for a
-4-day workshop as it is often used for online workshops. To use the custom
+4-day workshop as it is often used for online workshops. To use this custom
 schedule instead of the one provided by default in the template, delete the
-block of code found under the "Schedule" header and replace it with
-`{% raw %}{% include custom-schedule.html %}{% endraw %}`.
+block of code found under the "Schedule" header in the `index.md` file and 
+replace it with`{% raw %}{% include custom-schedule.html %}{% endraw %}`.
 
 The schedule is formatted using a table. If you would like to learn more about
 how to write tables in HTML, here is an [HTML table overview from