If you want your tlz packages to be listed in gslapt you will need to install them first.
Do the following steps:
1. Open your favorite terminal
2. Type "su" and login as root (su is like root but not needing to login separately as root)
3. Go to the directory where you have the .tlz packages and type the following as root: "installpkg name-of-file.tlz"
4. After it has been installed you can open gslapt and the package will be listed there.
Hope this helps you!