[FONT=Comic Sans MS]Featured Tutorial
Print Messages to yourself during runtime!
https://wiki.unrealengine./Logs,_Printing_Messages_To_Yourself_During_Runtime
I would like to thank JohnFlux for adding the section for on-screen debugging, I used it myself recently when logs and clientmessaging where both not options but I still had access to GEngine 
https://wiki.unrealengine./Logs,_Printing_Messages_To_Yourself_During_Runtime#Logging_message_to_the_screen