Your Timeline and each show's page always list the newest episodes first. To work through a show in order from its first episode, make a playlist sorted Oldest first.
With a smart playlist (Castria Premium)
A smart playlist fills itself with every episode of the show and keeps up as you listen.
- Open the Playlists tab and tap + New playlist.
- Give it a name, choose Smart, and tap Create.
- Tap + Add condition, choose SHOWS → In set, and pick the show. Optionally add STATUS → Unplayed so finished episodes drop off.
- Set SORT to Oldest first, then tap Create.
With a regular playlist (free)
- Open Playlists, tap + New playlist, choose Manual, and tap Create.
- Add episodes from the show with + → Add to playlist on each one.
- On the playlist, tap ⋯ and choose Oldest first.
Tap Play all on the playlist to start listening.