Export Your Podcast
Once you've created your mix, you need to export it into a format that anyone can play. But before you do that, you can use GarageBand to automatically optimize the audio level of the project. To do so, go to the top menu and choose GarageBand:Preferences. Click the Advanced panel and make sure that Auto Normalize is checked. This will help ensure your podcast is set at a good audio level. Also, below that is the Audio Resolution menu. It defaults to Good, but you can increase quality to Better or Best. Keep in mind that this will increase the file size.
While you're in the Preferences panel, click My Info. Here you can fill in some general info about your podcast, tags that will show up in iTunes. These include the name of the GarageBand project playlist in your personal iTunes, your name as artist and composer, and the "album name," which would also be the general name of your podcast in the iTunes podcast directory.
Close the panel. Back in the GarageBand Window, click that very top Podcast default track. If it's not there, go to the top menu and choose Track: Show Podcast Track. In the Track Info panel in the lower right corner, you can fill out information specific to this podcast episode, such as title, parental advisory, and description. This info will be embedded in your final podcast file.
Also, when the Podcast track is selected, a window will be visible in the lower left corner of the Editor. If you want to add an image to represent your podcast, you can drag an image file into the box.
To export, go to the top menu again and choose Share:Export Song to Disk… Choose the file format you prefer: MP3 or AAC. AAC is the default audio format of many Apple applications like iTunes. But MP3 tends to be the default format for most audio downloads and can be read by many more programs and personal music devices.
When you click Export, you can name the file. Be sure to use a name that makes sense.