So-called browser hi-jackers seem to be prevalent. These software's insert themselves into your browsers and take over as your primary search engine in order to get paid by any of your click-thru's. Some can intentionally be a real pain to remove, so carefully read the install screens. Just decline anything other than what you mainly requested.
If you still clicked and installed the crap-ware by mistake, then start with your uninstall programs feature of your operating system. In Windows, you can find it under the Control Panel labeled "Programs and Features". You may also need to run an anti-malware program like the freebie from Malwarebytes, which should likewise become a periodic routine. After you get rid of the crap-ware, it's also a good idea to run a registry cleaner like the freebie CCleaner (which originally stood for crap-cleaner) to get rid of any residual crap.