First, check MyCSUSM to verify you have been officially assigned the course. If you do not see it there, contact your department. If you do see it there, were you just assigned? It can take up to 24 hours from when you are assigned the course in MyCSUSM to when you get added to the course in Cougar Courses.
If it has been over 24 hours from when you were assigned in MyCSUSM, the course is likely under the Hidden Courses tab near the bottom of your My Courses page. Once you find it, click the star in the upper right to favorite it and bring it to the top of your courses list.
You can also access an alternate list of your courses which might make it easier to look through your courses. On your My Courses page click the Dashboard link under your name in the upper left. At the top of the Dashboard you will see recently accessed courses. Below that you will have your entire list of courses. At the top of the list, on the left you can filter by status (All, In Progress, Future, Past, Starred, and Hidden). And on the right you can switch the view from Card to List, which will make it easier to look through.