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

https://hectorgcbc844.theburnward.com/gatwick-airport-public-transport-your-complete-options-guide

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.