This can be done in different ways:

1. By booking an appointment directly at the German Embassy in London, You can book an appointment every working day from 9am to 10am except on holidays.
2. 2. Through VFS Centres in London and Manchester. German visa applications for UK residents are to be submitted at the Germany Visa Application Centres in London. All applications will be assessed by The Embassy of Germany, London.

Read more – Germany Schengen Visa