The default username and password are both backuppc. Edit
/etc/BackupPC/authUser to change these to your preferred values using the
htpasswd2 utility, such as:
# htpasswd2 -c /etc/BackupPC/authUser admin

This will prompt you for a new password and change the username to admin.
\`man htpasswd' for more options.

Please make sure to edit /etc/BackupPC/config.pl to suit your needs. If you 
change the username or want the backuppc user to have admin rights in the web 
interface be sure to change \$Conf{CgiAdminUsers} to the correct value.

To add backuppc to your default startup scripts run:
# rc-update add backuppc default
# rc-update add apache2-backuppc default

Then start it with:
# /etc/init.d/backuppc start
# /etc/init.d/apache2-backuppc start

Navigate using your webbrowser to http://localhost:28000/BackupPC_Admin 
for the web interface.