To save a project, click on the File menu on the Editor tab, above the source editor. In the File menu, select Save Project.
When you save your project, the save dialog will allow you to specify both a Project Name as well as a Display Name. The Project Name is the internal name of the project and is limited to lower case alphanumeric characters. The Display Name is what will be displayed as the title of the project in the file manager tree on the right of the editor.