So, let's see an example. let's suppose you want to install transmission, a light-weight BitTorrent client.
Step one: find and install a packageThis one is simple: if it's pre-compiled you can find it in your install CD/DVD, in the online Slackware mirrors (my advice is to search the package name in the list of packages, like this one) or on slacky.eu where you should search the package name in the right repository (in my case, 13.37 32bit). There it is:
Once downloaded, run as root installpkg to install it:
# installpkg packages/transmission-2.42-i486-1sl.txz
Verifying package transmission-2.42-i486-1sl.txz.
Installing package transmission-2.42-i486-1sl.txz:
# Transmission (GTK+ Lightweight BitTorrent client)
# It features a simple, intuitive interface on top on an
# efficient cross-platform back-end. Gtktransmission is open
# source (MIT license)interface). and runs on Mac OS X (Cocoa
# interface), Linux/NetBSD/FreeBSD/OpenBSD (GTK+ interface)
# and BeOS (native interface).
Executing install script for transmission-2.42-i486-1sl.txz.
Package transmission-2.42-i486-1sl.txz installed.
Step two: find missing software and librariesIf trying to run your newly installed software ends up with an error like this...
transmission-gtk: error while loading shared libraries: libevent-2.0.so.5: cannot open shared object file: No such file or directory
... you're missing someting. Let's find out what, running ldd on where the main executable script is placed (usually /usr/bin/).
:~$ ldd /usr/bin/transmission-gtk | grep not
libevent-2.0.so.5 => not found
There it is: libevent is missing. It's a library, so it could be contained in a package named in some other way, but a quick search for "libevent-2.0.so.5" on pkgs.org will tell you the package name you need. In this case, libevent.
At this point another search on slacky.eu and you will get your missing package:
Done! Now you have all you need to run transmission-gtk. :)