Facebook and social networks access bloking

Hi everyone, I’m from Venezuela and I have a RB433AH routerboard managing my network. I’ve been trying to enable blocking access feature of some pages through firewall rules and mangle with Layer 7 protocols, but I have no success in that goal, so, I want to know how can I do to enable that feature on my RB. If anyone in this forum can tell me that, I will really apreciate that help. so, thanks for any solution someone can give me..
Cap1.png
Cap2.png
Cap3.png
Cap4.png
Cap5.png
Cap6.png
Cap7.png
Cap8.png
Cap9.png
Cap10.png
Cap11.png