IRTS is Indian Railway Traffic Service. To get into this you have to take the All India CIvil Services Exam (IAS,IPS wala exam) conducted by UPSC. The Prelims are held in June , Mains in Nov - Dec and the interview in Apl-May next year. Final result is out in late May / early June. Your rank has to be high enough to get into Central Services Gr A list (Customs , Income Tax , Railways, Postal etc). There are 4 services of the railways IRTS, IRAS (Accounts), IRPS(Personnel) and RPF(Rly Protection Force). Look out for ads in Emplyment News and find out more from UPSC website.