From the Apple Wallet app:
1. To get started, open Apple Wallet on your iPhone or Apple Watch, or select Wallet & Apple Pay in System Preferences on your iPad or Mac.
2. Tap the + Button and follow the instructions.
From the NBX app:
1. In the NBX app you can select Card in the menu then you have the option to add to Apple Pay if you are using an Apple device to run the app.
In-store
With iPhone, double-click the side or Home button,
authenticate with Face ID, Touch ID, or your passcode,
then hold your device near the reader to pay.
With Apple Watch, just double-click the side button,
then hold your device near the reader to finish your
purchase
Apple Pay, is a mobile payment solution that is contactless and enable customers to make purchases both physically in stores or through apps or websites. Where contactless payments are accepted you can use Apple Pay.
You need a iPhone, iPad, Apple Watch or Mac-model that is compatible with Apple Pay. See the Apple support documentation about this here.
As Apple writes on their Apple Pay site: No. Apple does not charge any fees when you pay with Apple Pay — in stores, online, or in apps. And Apple doesn’t charge interest or fees when you use Apple Pay Later. (source)
Tap the add button in the wallet app then tap Debit or Credit Card (NBX VISA is a Credit Card) to add a new card. You can also follow the Apple support guide for how to do this.
See this guide for how to pay with your iPhone or Apple Watch or using Apple Pay online or within apps.
You can add up to eight cards to Apple Pay per device
If you lost your iPhone with Apple Pay installed you can use Find My device and suspend Apple Pay by placing your device in Lost Mode. See this article under the segment "If you lose your device and need to suspend or remove cards from Apple Pay".
In the wallet app, tap the card you want to remove. Tap the more button, then tap the Card Details. Scroll down and tap Remove this Card. You can also follow the Apple support guide on how to do this.