The Virtual Box console displays a linux terminal. You are wanting to perform bash shell commands as described in the "Customizing Security Requirements" mini-course. [email protected]/install is how you log into Pega through a browser aimed at the prweb webapp.
The root password is "password". As root you can change the password of any user.
EX: sudo passwd architect
The above will ask for the root password, the prompt you for a new password for the user named "architect".