As magicniner says, the manufacturer is the first place to ask, followed by the bearing manufacturer.

However, the general process will involve running at gradually increasing speeds with no load for periods of time, while monitoring the temperature.
If you read the last paragraph of this post - http://www.mycncuk.com/threads/10344...8817#post88817 (should be post 36 in the thread..) it describes how I ran in my Triac spindle after changing the bearings. You'll obviously want to adjust the chosen speeds to something a bit more suitable, as the Triac spindle is only rated to 3000RPM.