This might help other applicants.
I attended my biometric appointment yesterday for a British citizenship application (Tier 2 (5 years) and ILR (1 year)). The whole process took only 1 hour and it is very straight forward.
1. Inform your appointment at the reception upon arrival.
2. Collect your ticket (numbered) and wait in the room.
3. Your ticket number will be called and join a group.
4. A team member will give 2 mins instruction about the self-enrolment biometric process.
5. They will allocate you a self-enrolment biometric booth.
6. Step one - you need to scan your barcode that is on the appointment confirmation letter.
7. Next step - scan your passport photo page, then scan right-hand 4 fingers, right-hand thumb, left-hand 4 fingers, and left-hand thumb.
8. Next step - photograph, a camera will adjust automatically to take a standard photo (you re-take many times until it will fulfill standard photo requirements).
9. The last step - sign on the signature pad to complete the self-enrolment and submit.
10. Inform a team member and sit in the waiting room.
11. Again your ticket number will be called and take you into a case manager bay.
12. A case manager will review your application and make sure you have submitted all the documents. Also, they scan the passport copy again and upload onto your application.
13. Finally, they submit your application and all done.
P.S. I double checked with the case management team about the passport copy upload. The requirement is a cover page, photo page, all stamped pages, and the address page (no need to upload blank pages). Also, they haven't verified any of my original documents and I took it back all my original documents including my passport and ILR.