QR Codes means (quick response) codes are little black and white squiggly barcodes that usually look something like this: 

Selecting a QR Code Generator:

There are a lot of QR code generators available online, but a few of the post popular:

Kaywa

GOQR.me 

Visualead

QR Stuff

looking for when choosing a QR code generator are whether you can track and analyze performance if it allows you to design a code that's unique to your brand and if it is compatible with common QR  code readers. 

Desing and linking the website with the QR Code: 

In this example http://goqr.me/ is used for generating the QR Code. 

Put QR codes in places where scanning is easy and there's enough time for the consumer to actually scan the code.