Hello!, I'm just begening on the flight with the B757-200 :-/
I try to get into F / P (with RouteFinder)! all others informations are entered in the FMS .. leg set, all procedures have been completed! .. ect! but after "align my IRS (10 minutes), and pass on the NAV mode I have a message Wich FMS tell me! .." "IRS enter your position." How to proceed the operation ..! please!
   (sorry, this is a simple operation, but I can not find in operating manuals Captain Sim)
thank you and good flights! :)