Depending on your location, you will need to visit either a UK embassy or a visa application centre to have your biometrics taken.  Trained staff will take your biometric data.  A list of visa application centres can be found on this website.

If applying in the USA, you will need to attend an Application Support Center operated by the Dept of Homeland Security. Applicants in New Zealand should attend the New Zealand Department of Labour offices in Auckland, Christchurch or Wellington.  Applicants in Bermuda attend an office of the Govt of Bermuda to register their biometric data.