To pause a download while in progress:
- Tap on the FrostWire logo in the upper left corner to access the 'Main Menu'
- Tap 'Transfers'
- Tap on the 'Down Arrow' to the right of the file download you want to stop
- Tap on 'Pause Transfer'
Keep in mind that Transfers from the BitTorrent network can be Resumed in the same way, but Transfers from YouTube and SoundCloud will what to be canceled and started from the Search screen again.