You must create a module before you can add topics. You can create submodules (modules within existing modules) to establish a deeper hierarchy.
If your course is SCORM 2004-compliant, new modules that you create are outside the sequencing and navigation built into the SCORM package.
To add a submodule, click into the module. In the Add a sub-module field, enter the name of your new sub-module and then press Enter.