MacBook Air :: How To Remove Ads That Open New Windows

When I use the internet, if i click on anything to type, like the search or a login bar to my uni student account, or to my online banking account, it without fail, redirects me to another window. The other window most commonly is a mac keeper add telling me that I need to clean up my Mac as they are trying to get me to download something. I can exit off this window, and I go back to the other window. The other common one which is extremely frustrating is one saying that something has been detected blah blah blah, but it won't let me exit it from it. This gets annoying especially when I am writing papers for uni, and I have to shut down all my sources just because of one stupid pop up. I have also noticed that Netflix now had a bunch of pop up adds as well. I am very careful with what I put on my computer as I know you can get viruses from internet downloads. It all started when I let my lovely sister use my computer for a bit, but apparently solitare is not a cool enough game for her, so she downloaded that imvu game. After that, that's when I noticed all the pop ups and what not. I deleted it hoping that the ads would go away, but it didn't work. They are still there. How do I fix this because it is SO annoying. (it's a MacBook Air, has the mavericks operating system thing, processor 1.4 Ghz Intel Core i5, OS X version 10.9.6.

Info:
MacBook Air, OS X Mavericks (10.9)