newbie question about installing the newest versions

[Nhi]

Hey my question is about installing the newest version of debian packages through synaptic, i know i need to add some url for the sources list, but the url i added didn't work it was of us debian etch, it said i didn't have a public key.
I found the url at wesnoth site trying to upgrade the version of the game.

the url for the instructions
http://www.wesnoth.org/wiki/WesnothBinariesLinux#Ubuntu

the url for the debian packages
http://http.us.debian.org/debian/

This is my first post i would be glad for an answer...
Thanks anyway
Nhi

[900i]

The sources.list entry should read

deb http://http.us.debian.org/debian/

and not

http://http.us.debian.org/debian/

then save and do a

sudo apt-get update in a terminal before installing the software.