If the URL is static, and does not need to be changed functionally, you could consider using a static image instead of the QR Code widget, like Parth suggests in his answer.
If you do want to use the QR Code widget, you need to have a dataview on your page, containing an entity that has a string attribute. This string attribute can be used as the input for the QR Code widget, and should contain the URL to the page you wish to show. (You can set the URL of a page in the page properties tab).
The widget will display the QR code on the page, and when a user scans the code he can choose to navigate to the page. (make sure acces rights allow showing the page).
So the QR code is generated based on the text or link you want it to go to. Go over to https://www.the-qrcode-generator.com/ you will be able to generate the QR you want and you can use it too over your web or mobile app.