Whem I recive a Radio message, how and where can I read it??? How it works?
Make sure you have a radio operator on duty, that small room in front of the control room. You must be at a depth of periscope depth and above (on the surface). these guys will inform you of a message received. Press "M" (default key) to view messages.
When on patrol, do more listening than transmitting(sending messages). If you get too 'chatty', you'll have lots of escorts and ASW aircraft to talk to.
In truth, since there are no Allied Uboats,there is no reason to send a radio message. Only time a contact report is useful is when you are in rage of air support. Otherwise remain silent.