Launch iTunes, click on the file you wish to compress and select "Get Info" from the "File" menu. Look at the "Bitrate" of the MP3 file and write it down. Bitrate is a measurement of MP3 compression. Lower numbers mean smaller file sizes.
Open "Preferences," select "General" and click on the "Import Settings" button. Change the "Import Using" drop-down menu to "MP3 Encoder." Click on "Settings" and select a lower bitrate for your file. If no lower setting is available, click on "Custom" to choose a bitrate lower than 128 kbps.
Click on "OK" to confirm your changes, and exit the preferences. Select the file you wish to compress, and choose "Create MP3 Version" from the "Advanced" menu at the top of the screen.
Open AudioConverter Studio, and choose the folder in which the MP3s you wish to convert are located. The program will compress all of the files in a folder, so move any MP3s you don't want to change to another location.
Select "MP3" from the "Output Format" menu on the right side of the screen. Look in the "Files" menu with your MP3s, and note the number in the "Info" column. This value is the current bitrate of your files. Choose a lower bitrate from the drop-down menu on the right side of the screen.
Choose an output folder for your compressed MP3 files in the "File" menu. Click on the "Convert" button to the right of the "Output Folder" menu, and wait while the program compresses your MP3s.
Open Audacity and select the MP3 you want to compress in the "File" menu. Look at the file's current compression settings under the file name in the lower left corner of the window. Open "Preferences," and choose the "File Formats" tab. Under "MP3 Export Setup," select a lower bitrate than the current file. Some versions of Audacity have a "Quality" slider that shows you the file size of the new MP3 so you can set it to under 7MB.
Choose "Export as MP3" from the "File" menu, and choose a location for the new MP3 file.
Close Audacity when the export is finished. The application will prompt you to save your work, but it is asking about the editing project and not the MP3 file. You do not need to save your work unless you want to edit the MP3 again later.