Select Project → Project Properties... to display the Project Properties window.

Right-click on the required group, in the List of Entries pane, the left pane, that defines the build stage that you want to modify, for example *COMPILE=arm, and select Expand whole Tree from the context menu.

You can also expand, and collapse, groups in the List of Entries pane by clicking on the plus sign, or the minus sign, at each node in the tree. If you double-click on the group name, this expands the group and displays the contents in the Settings Values pane.

Select the *Sources group in the List of Entries pane to display the contents.

Right-click on the default Files setting, at the top of the list, and select Edit as Filename from the context menu.

This displays the Enter New Filename dialog box where you can locate source files to add to the project. Select the source file you want to add and click Save.

Alternatively, right-click on the default Files setting, at the top of the list, and select Manage List... from the context menu. Use the Settings: List Manager dialog box to modify the source list as required. You can also use this dialog box to add more files to, or to remove files from, the group. Click OK when you have finished adding files using the Settings: List Manager dialog box.

Select File → Save and Close to regenerate the makefile(s) for the project, and close the Project Properties window.

Select Tools → Build... to rebuild the application.