Sometimes it can be difficult to find a podcast RSS feed.
In that case, if all you have is the Souncloud Url, you won't be able to subscribe to the podcast in Podcast Addict, because the app only supports RSS feeds.
You can use the GetRssFeed.com website to retrieve the podcast public RSS feed url.
Just go into http://getrssfeed.com, paste the Soundcloud url of your choice (ie: https://soundcloud.com/shaneandfriends) and it will display the public RSS feed (ie: http://feeds.soundcloud.com/users/soundcloud:users:44683272/sounds.rss).
Now you just have to copy/paste this RSS feed url in Podcast Addict and you're done.