Google Chrome Extensions?

I downloaded some extensions but I can't get them to work. They have worked before except I uninstalled it at one point and then reinstalled the browser (I am using the latest version). I see the extensions in the wrench-tools-extensions menu but I do not how to actually use them. And I tried ctrl+alt+B.|||maybe just try redownloading them. This happened to me, and it was really obvious, because I use adblock and there were ads everywhere, but then after I reinstalled it, it all worked fine.