how to use it?
If you're running windows 8 (if not ignore the following step):
You're going to have to open Windows Defender and add the HOST file to the exceptions. Once you have Defender open, go to the settings tab. Afterwards, go to the "Excluded files and locations" column. You want to browse to "C:\Windows\system32\drivers\etc\hosts", click Add, and then save.
You want to open Notepad as administrator and open the HOST located in "C:\windows\system32\drivers\etc\hosts". Overwrite the content of the file with the text here (http://winhelp2002.mvps.org/hosts.txt). Save the file and restart your computer. You should see that there's no more ads (for the most part) on any application.