This solution article explains how to enter the Raspberry Pi Terminal:
Connect a keyboard and a USB drive to the Raspberry Pi.
Quick 'p: You can hook up a small USB-hub to the front of the printer to connect the keyboard and USB drive for easy access without the need to remove the back cover of the printer.
Press simultaneously Ctrl + Alt + F1. A text console should appear.
Enter the log-in credentials: Username: "pi"
Press Ctrl + Alt + F7 to return to the graphical interface.