Navigate to the course by selecting Find | Courses from the left nav panel and search for the course you want to edit (you may need to search in All Time Periods). When you find the course you are looking for click Edit. From here you can edit the Name, Course Code, the course's Course Group, Course image, Description, Additional info (you can also add additional info to individual classes in Edit Class), Grade minimum and maximum for the class, Course prerequisites, Deposit amount, and Course Fees.
Please note, if you change the course fees this will only apply to future classes created in this course. If you want the new fees to apply to current classes, you need to click Copy Course Fees to Existing Classes. This article explains more about this.
Any changes (other than the fees) you make at the course level will then automatically apply to all classes that have been built from that course, for past, current and future classes.