Once logged in, on the right side of your main page you will see "Course Catalogue" (see picture). When you click on it, you will be able to access all the courses, read the abstracts and start the courses you are interested in. You can then search courses by category of topics or by keywords.
Another option before you log in is to look at the very top of this page. You should see "Course Catalogue".
Or you can use the shortcut below. ;)