Unfortunately, you can't record programmes on the BT Sport App. However, the Apple and Android versions of the app contain On Demand catch-up of some programmes that you may have missed. This isn't available on the Windows 10 version.
If you have a YouView+ box, you can set a recording from your mobile device.
The YouView app gives you access to the TV guide over the next 7 days, and lets you record a programme from the TV guide while on the move.
The YouView app is compatible with iOS and Android.