if you want to convert some part of audio from the au file, drag the slide bar directly, or click the play button to preview the media file, set the start time and the end time. at last, click the convert button to start to convert au to mp3.

How would the previous sentence be correctly capitalized?
If you want to convert some part of audio from the au file, drag the slide bar directly, or click the Play button to preview the media file, set the Start Time and the End Time. At last, click the convert button to start to convert au to mp3.