Download the Vm .vdi image file from the https://www.linuxvmimages.com/

1. add the imgage .vbox from the virtual box manager

username : centos
password : centos

2. if you like to reset the password of the username

enter the 'e' keyword when it's booting time

and at the end of the line [ quite splash rw init=/bin/bash ]

now press ctrl + x save and enter to the safe recuse mode

3. here go to the 

$sudo su -i

$passwd centos

$exec /sbin/init  --> this reboot machine