In order to get rid of dnsrsearch.com, you need to open the settings of your Internet connection (on the computer or router) and change the DNS server settings. I recommend using DNS server from Google (188.8.131.52) or OpenDNS.
If you’re seeing unwanted pop-ups or ads in your web-browser, you might have an adware installed on your computer. Use the following guide to stop pop-up ads and remove malicious software. Or ask for help here.