When a Podcast is added to your Blog, RapidWeaver inserts any custom RSS tags defined in the your blog's Setup... area. You may override these RSS tags by using the Custom RSS Tags tab to customize any of the tags that RapidWeaver automatically inserts in your Podcast. Click the (+) button at the bottom of the "Custom RSS Tags" list and add any custom tags as required; to remove a custom tag, select it in the list and click the (-) button.

Blog - Podcast: Custom RSS Tags

You may also override the default Podcast settings on the Custom RSS Tags panel to link to external media files for your Podcasts (rather than using the Podcast dropbox), or to use multimedia types not directly supported by RapidWeaver. Click the "Override default Podcast settings" checkbox to enable these fields and fill in the URL to the media file, specify its size (in bytes) and its file type. When published, the file specified will be linked to your Podcast. For more details, see Podcasting with RapidWeaver in the Tutorials area.
When you are satisfied with your settings in the "Add Podcast..." pane, click the "OK" button to save your settings and close the pane. A dialog box will appear asking if you want to add a link to your Podcast in your blog entry.

Blog - Add Podcast Link

Click "OK" to add a text link to the end of your blog entry, and click "Cancel" if you don't wish to add a link.