Click the
Open or Open > In Default Tool button on the Home ribbon tab.Select the Open item in the selected business application's context menu.
Double-click the selected business application in the object navigator's folder tree.
Creating an internal structure of business application is executed in the BA Internal Structure folder, which is created by default on creating a business application.
The folder with business application internal structure is used to place all custom and service objects of the application and it is not displayed for web application users.
Folders for business application internal structure are created in the system object navigator.
To create an internal structure of business application, follow the steps:
Open business application for view on the system navigator tab:
Click the Open or Open > In Default Tool button on the Home ribbon tab.
Select the Open item in the selected business application's context menu.
Double-click the selected business application in the object navigator's folder tree.
Select the BA Internal Structure folder.
To create a new folder:
Click the 
New Folder button on the Home ribbon tab.
Enter folder name.
To create a nested folder, select the parent folder and create a new folder in it.
NOTE. To move the created folder to another location, drag and drop it.
After the application internal structure has been created, add objects to internal structure.
See also:
Building Business Application | Adding Objects to Internal Structure