server on mikrotik

Hi!
I have problems whit mikrotik and i hope you can help me?
I wont to make a Call of duty server on one comp. on my local network the comp. IP is 192.168.50.155 and the networks routers (mikrotik) IP is 192.168.50.1.
Now i conect to internet trough PPPOE - the IP on PPPOE is 10.1.1.10.
Now i wont to forward port 28960 so the people from external IP (73.5.126.398) can reach me on my servers IP 192.168.50.155

Can you help me ,what can i do to this make it work?
Tanks!!!