You can see courses in which you are an instructor or participant in the course overview (1) after logging in onto the dashboard.
You can return to this view at any time by clicking Dashboard (2) on the left side in the Navigation block.
Use the My Courses overview (3) to access course rooms directly.
Find more courses with the course search (4), in the search field Search courses you can search for the name of the course, the lecturers and words in the course description.

Another possibility: On the start page you navigate to your course via the course areas.