how do I get rid of malware?

I have some kind of malware present on my MacBook Air from trying to download a "flash player". I get full page pop-up ads for "mackeeper" and the like nearly every time I click on a link, have annoying ads on pages that I know weren't there before I downloaded this "program", and am now seeing other pop-up ads. As soon as I downloaded this program, my search engine changed to "Conduit", if this info helps.What can I do to get rid of this?