I'll be walking through screens showing AdBlock Plus on Chrome, but it is available for other browsers as well as Android.
The easiest way to install it is to visit https://adblockplus.org in the browser to which you want it installed and follow the instructions.
Once you have it installed it starts working immediately to remove ads! How sweet is that?
It isn't perfect however, as webmasters have figured out a variety of tricks to avoid adblockers. Not a problem. See the video clip below on how to manually remove ads or other irrelevant content from the sites you use.