By clicking on the "Scene(s) to apply" button you can see those scenes, which are open to apply for. (Professors can set a deadline to apply for certain scenes. Usually there are a small number of scenes that you can apply for, because the scenes of the courses that you have applies for in you institute have been automatically added to your CooSpace.

If you want to apply to a scene, click on its name, and after that on the "Apply to the scene" button. 

After your apply, the scene will be added to the list of "Pending scene(s)", which is shown above your current scenes on main page. The professor in the scene will decide wheter he/she accepts your application or not. You will get a notification about the decision through the email notification system.