Many of the free apps are AD-SUPPORTED so I'm guessing you meant AD rather that "add". The way to block them is just like we heard before, long ago -> "The only winning move is not to play."
Android is very open to such annoyances and if you have an app that annoys you, uninstall it.
I just got my brand new samsung galaxy note 10.1 and ive installed a few apps here and there and more or less every time i play a game i get these annoying app pop ups and even ads while im on the main screen with free download here and there etc. Is there a way to block these away?