If you applied for your visa overseas, this requirement will be printed on your 30- or 90-day entry clearance sticker in your passport. Visit Gov.uk for further details.
If you applied for your visa in the UK, this requirement will be printed on the letter you were given when you received your passport and documents.
Please check carefully whether you need to register with the police, as the consequences of not doing so can be serious.
If you are based in London, registration is completed at the Overseas Visitors Records Office. You need to book an appointment online via the OVRO website. Please read the information on the OVRO website carefully about preparing for your appointment. Visit their website for further updates - Overseas Visitors Records Office.