Excuse me for my silly question.
"3.3. Using Sage" in https://wiki.sagemath.org/SageAppliance/SageMath-7 says that after the virtual machine has finished booting, you should see the following window:
But what I encounter is the following window:
I have tried entering the first two folders and opening the "notebook-browser" but I still do not know how to launch the Sage Notebook. Could anyone help me? I would appreciate any help with this situation.