If you’re new to London, follow “Trains to Gatwick Airport” signs at Victoria, London Bridge, or St Pancras

https://dominickmeoc438.cavandoragh.org/gatwick-airport-public-transport-your-complete-options-guide-1

If you’re new to London, follow “Trains to Gatwick Airport” signs at Victoria, London Bridge, or St Pancras. Ticket machines and staff can assist with route and fares.