I have now read the manual at http://www.mikrotik.com/testdocs/ros/2.9/guide/aaa_radius.php
And found this;
Here you can download MikroTik reference dictionary, which incorporates all the needed RADIUS attributes. This dictionary is the minimal dictionary, which is enough to support all features of MikroTik RouterOS. It is designed for FreeRADIUS, but may also be used with many other UNIX RADIUS servers (eg. XTRadius).
Note that it may conflict with the default configuration files of RADIUS server, which have references to the Attributes, absent in this dictionary. Please correct the configuration files, not the dictionary, as no other Attributes are supported by MikroTik RouterOS.
So my question has become how? MikroTik?