The process you will need to use depends on how it operates. For a lot of malware or adware, it typically comes in when you install an already infected application from the Internet.
There are a lot of people who intentionally propagate these infections through freeware or shareware on the Internet using "bundling". If you use Windows PC, freeware from the Internet may bring such adware or malware.
The first thing to determine is exactly what’s doing the redirection.
For example, if it’s your router, it’s not even your PC' fault, and it can usually be fixed by updating your DNS settings in the router, or having the ISP doit for you.
If it is caused by adware or, follow the steps below:
Uninstall suspicious programs from Windows Control Panel
Remove unfamiliar browser add-ons/extensions
Reset your browser settings to defaults or reinstall your browsers
or try the following free anti-malware programs:
Download and scan with AdwCleaner. Have it found something and deleted, then reboot => https://www.malwarebytes.com/adwcleaner/
Download & Scan with Junkware Removal Tool. Have it found something and deleted, then restart => https://www.malwarebytes.com/junkwareremovaltool/
Download & Scan with MalwareBytes Anti-Malware Premium 14-Day Free Trial. Property MBAM quarantine found everything, then restart => https://www.malwarebytes.com/premium/
Follow-up by doing a scan with malware removal tool (free virus scanner). Remove / delete everything that found itself, then reboot => http://www.okpckit.com/SpyHunter_Download.php