You will need first to set up Apple Pay. On iPhone, simply open the Wallet app, tap +, and follow the steps to add your credit or debit cards.
To enable Express Mode for Apple Pay take the following steps:
For iPhone:
- Open Settings, scroll down and tap Wallet & Apple Pay
- Tap Express Travel Card
- Select a card. You will then need to authenticate with Face ID, Touch ID or passcode.
For Apple Watch:
- Open the Watch app on your iPhone and select the My Watch tab.
- Select Wallet & Apple Pay, then tap Express Travel Card.
- Select a card, then authenticate with your Apple Watch passcode.
Find more information on Apple Pay on their website.