In the image above there is an orange circle.   It is highlighting what we call the "waffle" button.  Choosing this button should bring up the courses you are a part of.  Once registered you should be automatically be added to your Brightspace classroom.

If you don't see your course right away in the drop down menu then you can search for it by typing the course code in the search bar.  If you are taking summer school you can always try typing "Summer" and your course will likely appear.  You can always click the "Pin" icon after your course appears and it will show up at the top until you decide to "unpin" it.