Free M4a to MP3 Converter was designed to be intuitive, so normally you don't need to search for some specific option in menus and help. However, there are a few preferences that may improve your experience with the program.
Click "File" - "Options" to open options menu.
"Reset status of conversion when you press Convert" means (if checked) that the status of files in the conversion list will be reset to "Not processed" every time you click "Convert", whether they have been already converted or not.
"Auto clear list after conversion is done" will remove (if checked) all files from the conversion list after a successful conversion.
"Show message after processing file(s)" will show (if checked) a confirmation message after converting files.
Click "OK" to save your preferences and start converting your AAC, M4a, MP4, 3GP, M4b files.