How to get sudo privilage in debian lenny

Normally in debian lenny we can use only su to become the root ifwe nee to use the sudo power then we have to edit the /etc/sudoers file
first become root by using su

ganesh@debian:~$ su
Password:
debian:/home/ganesh# visudo

Now add the username to the list..
ganesh  ALL=(ALL) ALL

am attaching the scrrenshots