Make your image for where the code goes. Read up on Tesselator, you just bind the texture like any other image (look in vanilla GUI's for this). Go into Gui and look at how they use the Tesselator. fontRenderer.drawString is pretty self explanatory. Create a variable in your class with the type List and set it equal to and ArrayList. There is a method in Gui called keyPressed or keyTyped not sure which, but use that to write to your List.