In the Show Text event command, you can hit F1 to show everything you can do with that. In this case what you need is typing:
## is where you put the desired actor ID. Now in the game, if character 1 is named Test and you write \N or \N it will in the game change into Test. If you want to see how it gets directly in the editor, you can in the "Show Text..." command hit F2 to get a preview.
Hope I'm clear enough.