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You need to make sure the device is updated to the latest OS first. Then open the wallet app and tap the + symbol. That is how you get cards into wallet. However, if you are just looking to scan QR codes that link to things you need to install any one of the hundreds of QR scanning apps in the AppStore.
I would go with an app. Wallet doesn't recognize all QR scans. Here's a good free QR scanner.
Quick Scan - QR Code Reader by iHandy Inc. https://appsto.re/us/GkYZC.i