Sure, here are some steps you can follow to reduce the storage used by Podcasts on your iPhone:

1. Open the 'Settings' app on your iPhone.
2. Scroll down and tap on 'Podcasts'.
3. Tap on 'Download Episodes'.
4. Choose 'Off' if you don't want episodes to automatically download to your device. If you still want some episodes to download, you can choose 'Only New' or 'Only Unplayed' to limit the amount being downloaded.
5. Go back to the 'Podcasts' settings page and tap on 'Delete Played Episodes' to automatically remove episodes you've already listened to.

You can also manually delete episodes:

1. Open the 'Podcasts' app.
2. Navigate to 'Library' and then 'Shows'.
3. Tap on the show that has episodes you want to delete.
4. Swipe left on an episode and tap 'Delete'.

Remember, if you're streaming podcasts using cellular data, this could also use up storage space. To prevent this, you can change your settings to only allow streaming when connected to Wi-Fi. This option is also found in the 'Podcasts' section of the 'Settings' app.