When you’ve selected your MP3 file to upload to the media player, it will automatically appear on your project page. Keep in mind that files may not exceed 12MB.
Ways to Make Your Files Smaller
If your file needs to be compressed because it’s currently larger than 12MB, there are a few easy ways to do that. Free software programs like Audacity can help, but the easiest steps you can take use simple compression tools in ITunes.