Question

RouterOS Beginner Basics
1

I have router RB750 and I want to ban facebook and youtube until 14:00 o’clock.
Can you please tell me how to do it?
Best regards,

2 
/ip firewall filter
add action=drop chain=forward disabled=no dst-address=69.63.176.0/20 time=\
    4h-14h,sun,mon,tue,wed,thu,fri,sat

That should ban facebook everyday from 4 untill 14 o’clock.
YouTube uses Google IP Address Pool (209.85.128.0/17), so I am pretty sure that you won’t ban it.

PS: IP Address Pools may change anytime, so make sure that you keep that information updated.