Remember that you checked in the project to the Repository from the SSWE, so the view to the project files is read only. To modify a file, you first need to check it out.
To review how to check in a project from the SSWE, please refer to Checking In the project from the SSWE.
In the Project Editor
The file which you will modify is
In the Check Out dialog, press Exclusive Lock.
In the File List, notice that
To load the now writable
ansi.c file into the Source Editor, double-click on it in the File List.