You can get faster response for PowerPress issues at the blubrry.com forums, forum.blubrry.com.
Unfortunately, simply placing a URL to a media file is no longer adequate if you want to truly podcast. You can thank or blame iTunes, but in 2005 they setup some special specifications which, if you want to maximize your coverage on iTunes, you must use.
What PowerPress adds to your edit screen is a "Episode Entry Box", which is where you can paste your media URL and then click our 'Verify' button, which doubles as a method to check your URL is valid, as well as populate the extra meta data needed for iTunes. This extra meta data is the file size in bytes and the duration in seconds. In addition, you can customize PowerPress to specify specific values for other iTunes attributes, configured in the basic settings tab of PowerPress settings.
When migrating from an older platform where media URLs are placed in the blog post content, all you need to do is go to the PowerPress Tools page and select "Import episodes from Blogger and other blogging applications". When you view this page, you will see how it will map media files to each blog post. It adds logic to make sure you only add one media file to a blog post (doing multiple is problematic for iTunes and just about all other podcast catchers). Go to the blubrry forum for more info on this, lots of folks have used this for migrating from static sites, movable type, blogger, typepad, PodPrsss and many other blogging apps.