Console password for cisco router 3845

I configured a cisco router 3845 but i didnt do any configurations for the passwords.Second time i tried to login i had this message :

Cisco Router and Security Device Manager (SDM) is installed on this device.
This feature requires the one-time use of the username “cisco”
with the password “cisco”. The default username and password have a privilege level of 15.

Please change these publicly known initial credentials using SDM or the IOS CLI.
Here are the Cisco IOS commands.

username privilege 15 secret 0
no username cisco

Replace and with the username and password you want to use.

For more information about SDM please follow the instructions in the QUICK START
GUIDE for your router or go to http://www.cisco.com/go/sdm

Can anybody help me please how to reset the password or access it in order to put a new password for it??