restrict internet access via router

hello

we have got e mikrotik router with routeros v 3.10 .

I want to restrict network users in access to internet .
but i dont know how.

please help me.

http://wiki.mikrotik.com/wiki/Main_Page
http://www.mikrotik.com/testdocs/ros/2.9/
Or there are many people using this forum who would be able to provide consultancy services.