Steps after the appointment from the US for British visa, vfs global registry confusion?

Hello, I submitted my application for a British visa for myself and my wife. I booked the appointment and got to a page where I was asked to download files and register with our visa application center partner and buy labels. I clicked the "Register" button. I had to go to the VFS website. After I and my wife got together in a family group, I was asked to upload documents. According to the steps on the visauk website this registration part and the document upload part are not mentioned! What to do when this document is uploaded is also a certificate, although you have been living in the US since 2015.
Can anyone explain, is this registration optional or part of the steps?
What to do, since I do not have tb cert and i am in usa since 2015?
Note: I have booked my biometrics on uscis asc, no bonus.
Thank you for your help .