Please refer Host Header Attack previous post before reading this one
Steps to perform Cache Poisoning Attack:
Find URL in burp suite having status code 2xx | 3xx.
After intercepting the website, send it to intruder and change host to any website (Eg: Bing.com).
Click go and search in response for the website you have entered(Eg: here bing).
If found, Right-click where you changed the host name and click on "show response in browser".
Try every clickable item on the webpage, if it is getting redirected to a website( which you have entered in the host field) then there is a vulnerability.