Adding data to the Hosts file

I am trying to add data to the 'hosts' file. When I paste this sudo /Applications/TextEdit.app/Contents/MacOS/TextEdit /etc/hosts - into the 'terminal' I am asked for a password I don't ever remember setting. After resetting the password using the OS install CD I went back to the 'terminal' and typed in the password. Nothing appeared on the screen when I typed the password and after pressing 'enter' a message said it was the wrong password. Should at least some characters appear as I type the password or should the password be preceeded with another character or word?
The machine is a month old mac pro belonging to my 87 year old father in law who uses it with Photoshop. I am a Windows follower and know very little about OS X please help.

When you sudo - you won't see anything echoed back in the password prompt. If the command works - it will respond - otherwise you will get the wrong password message. One thing you can do is do a
Put in the password. If it works you will get a directory listing. Then you have a few minutes to do other sudo commands without having to put in the password. The sudo password is usually the same password as the login password - not the root password.

Sudo

Thank you IvanLasston it worked this time with the same (I'm sure) password I used before. It is a bit unsettling not to see anything happen when you type your password in under Sudo. My problem is now is I have to type in a password when I switch on the computer. There also appears to be the option to sign in someone else! I think this happened when I changed the passwords.
How do I get back to sarting the computer without having to login at all?
Thanks, Don