Well, does it even have one installed? Linux doesn't operate in "console mode" or "window mode", a GUI's just a program like any other -- it's quite possible you didn't install one.
Or maybe you meant that you have one, but it doesn't autostart. Hard to tell from your question, but since you say you're new, I'm guessing not.
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Google suggests
this. They're actually doing the opposite but it shows how Arch does it -- init 5 for GUI, init 3 for console