And in most cases tgz files are specifically for Slackware systems using the pkgtools to install, remove and upgrade packages.
If you installing a tgz on your Slackware system you can just download or obtain the package and do this to install it as root:
To remove you would simply:
And if you already have the package installed and you want to upgrade it by checking in your /var/log/packages directory to see if it is already installed, you would do something like this:
Note, this method will only work with the tgz files, not the tar.gz. tar.gz or source files will need to be installed the usual way of installing source files, etc.