To add files to the concatenated files list, press the Add button or Alt+A and select files you want to add to the list. You can do this several times to add files from different folders or disk or network drives. The added files will be placed at the end of the file list.
You can also add files by selecting, dragging and dropping them from the Windows Explorer. The dropped files will be added to the end of the file list.
Once you have added all the files you want to concatenate you can rearrange
the file names to control the order of concatenation.