Teacher, Course Creator, and Administrator roles are all responsible for adding courses to a Moodle site. Although teachers are an integral part of the process, they don't have permissions on the Teacher role to add courses unless the administrator changes the capabilities. If you're an administrator, and depending on the organization and how involved you are with the site, you may want to give the Teacher role the capability to add courses to save you time.
You can find a number of links within the Courses folder: Add/Edit Courses, Enrollments, Course Default Settings, Course Request, and Backups.
It's good practice to define a number of categories before you start adding courses. Moodle provides you with one category, Miscellaneous. You can name your categories anything you want, though it makes sense to follow either departmental listings or a logical and descriptive format that instructors and students will be able to easily understand.
To add a category, follow these steps: