QR codes can be scanned using a smartphone's camera, but for it to turn into a decoder, it first needs to be enabled.
Check within the settings of your smartphone's operating system or prefered browser if there is an option to scan QR codes. If there is, simply enable it.
Once the feature is active, simply place your smartphone's camera over the QR code and you will be redirected to its content in no time.
Alternatively, you can download one of the many QR code readers that are available for all operating systems, and most of them are free. You can check the ones that we recommend here.