To share the event stream load over several threads or processor instances, you need to adjust the segment count of said TEP.
If you start up a TEP for the first time, you can control the number of segments with the initialSegmentCount field.
If the TEP has already run (which I am assuming is the case), you will need to use the split functionality to split a given segment into several parts.
When using Axon Server, achieving this split is simply done by accessing the dashboard of the application in case and using the + button of the TEP you want to split for.
If you are not using Axon Server, you will have to invoke TrackingEventProcessor#splitSegment(int) on the right TEP by providing the identifier (read: the int) of the segment you want to split.
Trusting this helps you further Prashant!
PS. It is important to note that this mailing list will be discontinued as specified in this thread.
The thread also specifies where to look further for help when it comes to Axon as soon as this mailing list is closed.