using aptitude on Debian 5 (Lenny)

To me, using Linux is always difficult, having get used to FreeBSD...

I just don't undertstand why all those man pages could not be written with more examples...

anyway, i installed Debian 5 and wanted to install IPRAS.

aptitude could not find the package, but a search on google shows that the package exists..

http://packages.debian.org/lenny/irpas

This page advise adding "deb http://ftp.de.debian.org/debian lenny main non-free
" to /etc/apt/sources.list

but I think they miss out something.

This is what I added in my /etc/apt/sources.list :

deb http://ftp.de.debian.org/debian lenny main non-free
deb-src http://ftp.de.debian.org/debian lenny main non-free

I run "aptitude install ipras" and again it complained package not found

more googling for aptitude tutorial and found this

http://algebraicthunk.net/~dburrows/projects/aptitude/doc/en/ch01s01s05.html

so i must run aptitude and type u to do an update.

after the update, "aptitude install ipras" runs and ipras was installed!!!