Tap on the yellow reader at the start and end of each journey (except on buses/trams, where you only tap in).
You can buy a standard Oyster card immediately upon arrival in London at several locations: how to buy oyster card london
Over 4,000 local newsagents and shops across London. Tap on the yellow reader at the start
If you want to receive your card before leaving home, you can buy a online. Cost: The card itself is £10.50 (plus postage). how to buy oyster card london
Most suburban rail stations. 2. How to Purchase at a Ticket Machine Locate a yellow card reader on a ticket machine. Select "Get new cards" (or "Buy and Top Up"). Choose your initial top-up amount (e.g., £10–£20).