Add reference to library_content advanced setting

cms/templates/library.html

@@ -70,7 +70,7 @@ from django.utils.translation import ugettext as _
                     <p>${_("Add components to your library for use in courses, using Add New Component at the bottom of this page.")}</p>
                     <p>${_("Components are listed in the order in which they are added, with the most recently added at the bottom. Use the pagination arrows to navigate from page to page if you have more than one page of components in your library.")}</p>
                     <h3 class="title-3">${_("Using library content in courses")}</h3>
-                    <p>${_("Use library content in courses by adding a Randomized Content Block to your courseware, and enter the Library ID for each library from which you want to draw content. In the settings for each Randomized Content Block you can specify the number of problems to be randomly selected and displayed to each student. ")}</p>
+                    <p>${_("Use library content in courses by adding the {em_start}library_content{em_end} policy key to Advanced Settings, then adding a Randomized Content Block to your courseware. In the settings for each Randomized Content Block, enter the Library ID for each library from which you want to draw content, and specify the number of problems to be randomly selected and displayed to each student.").format(em_start='<strong>', em_end="</strong>")}</p>
                 </div>
                 <div class="bit external-help">
                     <a href="${get_online_help_info('library')['doc_url']}" target="_blank" class="button external-help-button">${_("Learn more about content libraries")}</a>