You will need iTunes installed on your PC/Mac. Locate the podcast in iTunes and subscribe to it. In iTunes, click on the "Podcasts" link under 'Library' on the left. Right click on the podcast and select 'Copy Podcast URL' from the menu to copy the podcast URL to the clipboard. Open a new browser window and paste the URL in the browser's Address Bar to see the RSS feed.
On your device, open BeyondPod and tap on "Add Feed" button located at the bottom right of the Feeds Screen. Enter the address from browser's Address Bar in the BeyondPod Search field and tap Go. BeyondPod will open its 'Add Feed' dialog where the correct Feed URL will be already set. Tap on 'Save' button at the bottom to add the feed.