Modules and sub-modules are created to organize course materials within the Content tool.
Before you can add topics (i.e. documents, images, media files, URL links, etc.) to your course, you have to create a module to hold them. Sub-modules can be created within modules to establish a deeper hierarchy.
Click on Content on the navigation bar.
Click on Add a module and type the name of the module.
Click on the name of the module to open it.
To add content to the module, click on New and choose the type of content that you wish to upload, or click on Add Existing Activities to link items from within your course to the module. If your browser supports it, you can drag and drop content from your desktop to the upload target (indicated by a box with a dotted border).
To create a sub-module, click on Add a sub-module.