Open the Logic 8 application on your computer. Locate the MIDI file and click on the desired track or region.
Click on the "File" option from the top toolbar menu and then click on the "Export Track as Audio File" option.
Enter a name for you file in the "Name" box. Select the folder where you want to save the converted file or click on the "New Folder" button to create a new folder.
Make any other changes to the settings to meet you preferences, such as changing the bit depth, sample rate, output and any other settings. Make sure to specify what type of audio format you want the MIDI file to be converted to.
Click on the "Save" button and your MIDI file will be converted to an audio format. Allow time for the conversion process to complete and then locate the converted file on your computer. Double-click on the file to make sure it converted properly.