When submitting a Student Visa extension application, if you have an iPhone 7 or newer or an Android phone with near-field communication (NFC), you can use the UKVI IDV app to submit your biometric information.
If you are unable to use the app, once you have submitted your online Student Visa application, you must book and attend a biometric enrolment appointment at a UKVCAS Service Point. You must attend your appointment with your confirmation letter with QR code, passport and supporting documents (unless you have already uploaded your documents when submitting your application online).
At your appointment you will show your passport to have your identity checked and enrol your biometrics (fingerprints, photo and digital signature) in the self-service booth.
Your visa application will not be processed until you have attended your appointment and enrolled your biometrics.