with a example to making repositories available for scribus to package manager: (by the way scribus is a really good free software, if you have it you don't need Adobe Illustrator any more. It is a replacement for Adobe Illustrator, like Gimp for Photoshop.)
Debian stable (Etch):
deb http://debian.scribus.net/debian/ stable main non-free contrib
deb http://debian.tagancha.org/debian/ stable main non-free contrib
Debian testing (Lenny):
deb http://debian.scribus.net/debian/ testing main non-free contrib
deb http://debian.tagancha.org/debian/ testing main non-free contrib
Debian unstable (Sid):
deb http://debian.scribus.net/debian/ unstable main non-free contrib
deb http://debian.tagancha.org/debian/ unstable main non-free contrib
Ubuntu dapper:
deb http://debian.scribus.net/debian dapper main non-free
deb http://debian.tagancha.org/debian dapper main non-free
Ubuntu edgy:
deb http://debian.scribus.net/debian/ edgy main non-free
deb http://debian.tagancha.org/debian/ edgy main non-free
Ubuntu feisty:
deb http://debian.scribus.net/debian/ feisty main non-free
deb http://debian.tagancha.org/debian/ feisty main non-free
by using GUI like Synaptic, do following:
1) Start Synaptic package manager or Synaptic
2) Click on "Settings" > "Repositories"
3) Click on "New" and type or paste in the "URI", "Distribution", and "Section(s)" and click on "OK"
4) click on the "Reload" button in the toolbar and wait for the package database update to complete.
5) Click on the "Search" toolbar button. A "Find" dialog window will open. Type "scribus" in the "Search" field and click on the "Search" button.