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When you load a course you only are able to view what has been added to it. In order to edit the content, click the gear icon 
and then Turn editing on buttonon located on the top right corner of the course.
After you turn editing on Edit menus and other options become available to you in the course, and the Turn editing on changes to Turn editing off.
To select the specific Activity/Resource to be added to the course, click Add an activity or resource (4) at the bottom of the specific Week or Topic section.
This will load the Add an activity or resource menu.
Selecting any 
To select an activity or resource from this menu will display a description of it on the right panel. After making a selection, click Add to load the setting for it to be added to the coursejust click on the icon you like. If you want to see more information regarding the activity before adding it to the course you can click on the "i" below each icon.