I don't understand how the GUItext thing is working. I have a new project with a GUItext assigned to a simple GameObject. The GUItext has some text but nothing is rendering on the screen.
I found some related topics but nothing specific enough.
I worked with GUI.Label() but it seems that the logic is different ? (you have to assigned the GUItext to an object)
The two things you mention there are as far as I know not really related.
For the GUIText you simply go to your scene and GameObject->Create Other->GUIText. This will create a GUI game object in your scene which is rendered.
The GUI.Label is something that you would place in a script. You create a JS script and put the folling in tehre (from the documentation):