Go2Linux shows you how to install packages in Slackware Linux

Slackware is the oldest Linux still being maintained, it is light, simple, and stable.
It is not too easy to maintain, specially because most Linux users now a day (me included) are accustomed to package manager tools that take care of dependency resolution. In Slackware the user is the one who should resolve this, and install any package or library needed.

  Slackware package manager - how to install applications