Today, in most of the advanced smartphones, the QR code reader already built in the camera App.
To scan a QR Code, just open your camera App, hold it in front of the QR code for 2-3 sec. you’ll receive automatically (without pressing any button) a link to the QR code destination.

On the other hand, if you would like to create a QR code, you can use one of the following QR code creators for free:

https://www.qr-code-generator.com/

https://www.the-qrcode-generator.com/

https://www.qrcode-monkey.com/