In the Window's Explorer, select the audio files you want to convert.

You can select the files by left clicking and then dragging over the file icons (When you are dragging it shows a big square). Or you can select the files by holding down the Ctrl key and left clicking on the individual songs you want. Or you can select a file at first, and then holding down the Shift key and left clicking on the individual song to check those songs between these two songs. The information of those files you have selected will appear in the Play-List, and then the system will convert the file in order unless you click "Stop" button.