First off, I want to thank everyone who makes GLFW! It's very nice and easy to use.
Now, I would like to know how to open full screen after I have opened the window. Do I just need to create another window in it's place?
Currently you have to close the window and re-open it fullscreen. See a similar question https://sourceforge.net/p/glfw/discussion/247562/thread/f4164722/
There is work in progress on being able to change the window from windowed to fullscreen mode dynamically here: https://github.com/glfw/glfw/issues/43