I’m a newbie, please Help 
My Question is very simple, how can i make a mac address filter, so only the computers that registered in the mac address lists can access the internet via the routerOS.
Thank you so much for your help.
Paul
One of the method to use static ARP table,
http://wiki.mikrotik.com/wiki/How_to_secure_a_network_using_ARP
I am assuming you are refering to wired clients…
Wireless it can be done via Authentication tables.
Craig
http://forum.mikrotik.com/t/how-can-i-block-the-host-to-access-internet/11144/9
some example
(use search)