Download a freeware, which turns out to contain malware. How to remove?

Hi, there! I downloaded a VLC player from the web since the old one seems to be outdated. I thought I got it from official site, but I might have made a mistake. When the download was almost complete, there was a massage saying that “would you like to download vosteran search”. Before I could decline it, the download was complete. Now, I have to start with it when opening up the browser.