Not able to edit code via Atelier

In order to edit anything in Atelier the  code has to be part of a project. To create an Atelier project right click and choose New->Atelier project.  Then you can right click the class or routine you need to edit and choose "copy to project".

Open the copy associated with the project to editit

To have a possibility to edit files, you have to create a project, and copy existed classes to this project.

You can look at this youtube playlist, to get more information about working with Atelier.