You can queue picture files for compression from the desktop using the “drag and drop” method, or from within QT Batch Compressor itself.
To compress files from the Finder, select the files you want to compress and drag them onto QT Batch Compressor’s icon or alias.  Compress all the pictures in a folder or disk at once by dragging and dropping the folder or disk icon.
To compress files from within the program itself, choose “Select files” from the File menu or the Settings dialog.  This will bring up a modified Open File dialog that lets you examine, add and delete files to the list queued for compressing.
When you wish to begin the compression process, press the “Compress” button.  Compression will operate in the background while you do other things.