On the Big Sandwich site copy the feed URL for the show you wish to add (it will look something like https://bigsandwich.co/feed/wplanet/). Then open Podcast Addict and then press the + button in the app to add a new podcast. Paste in the feed URL and select the option to use ‘Authentication’ and then enter your username and password.

If you are using an older version of Podcast Addict which doesn’t have the Authentication option you will need to follow the instructions in the ‘How do I add the podcast feeds to Pocket Cast and older versions of Overcast and Podcast Addict?’ section.