Both settings are in Settings → Downloads.
Open Settings: on a phone, tap the menu button (☰, top right) and choose Settings. On a computer, Settings is in the bar across the top. Under Downloads:
- Download over WiFi only: automatic downloads wait until you're on WiFi. If you start a download yourself on mobile data, Castria asks first.
- Minimum free storage (Off, 500 MB, 1 GB or 2 GB): automatic downloads pause when your device has less free space than this. Downloads you start yourself aren't affected.
To free up space now, turn on Delete after played or Limit downloads per show in the same section. See How do I control automatic downloads?