This task can be accomplished by setting coma separated values for ListenPort property in "engine.properties" file:
ListenPort = 8901,8902
In this case engine will listen for incoming connections on ports 8901 and 8902. Note, all clients will be able to connect to any of those ports with correct login credentials of any acceptor session.
If you need to specify a dedicated port for each acceptor session, you can just give one client one port (say, 8901) to connect and give another client second port (say, 8902) to connect, etc. Hence each will have acceptor session working on dedicated tcp port.
For more details about FIX engine parameters, please follow this link - FIX Engine parameters.