Method #1 adding the contents of a folder. Select the folder files from which you want to add and press the "Add all files to Selection List" button () on the Folder Panel toolbar.
Method #2 adding separate files. Select the necessary files from the selected folder at the File Panel and press the "Add selected items to Selection List" button () on the File Panel toolbar to add these files to the Selection List. Double-clicking the left mouse button will also add the selected file to the Selection List.
Method #3 adding all the files from the specified folder.Press the "Select the folder to be added" button () on the Selection List toolbar.