I've had a bit of experience with game maker. To show text in the room, goto the draw event of any object and either use the [Draw Text] D&D object (located in draw menu.) or use a code object and type the following code:
Code:
draw_text(x,y,"Text you would like drawn");
Also, be sure to read the help file. It could have answered a question like this.
For anyone that is not familiar with gamemaker, see
this link if you are interested.