Launching a .kit file is OS and desktop environment specific. This page can, at best, cover the basic high-level concepts.
There are several ways to launch a .kit file on a Linux OS. Several possibilities are:
From the command line. Open a terminal/xterm/rxvt (or whatever your favorite Linux distribution terms a command line terminal) and launch the kit by giving the name of the proper TclKit executable followed by the name of the .kit file on the command line. E.g.:
./tclkit-8.6.6-Linux gorilla-1.6.0-beta-1.kit
Note: The above assumes that the executable and .kit files are named as shown above (substitute the names you have chosen instead), that they are both in your current working directory, and that you have set the executable bit on the TclKit executable. (Search the internet for information on how to use the 'chmod' command if you do not know know to turn on the executable bit).your executable PATH variabile contains your current working directory.
Depending upon what desktop environment you use, you may be able to associate files ending in .kit with the TclKit executable file, and thereafter be able to launch the .kit by simply clicking upon the file. How to do this is desktop environment specific so you should search the internet for instructions on how to do this if you do not already know the answer.
As well, depending upon your desktop environment, you may be able to drag and drop the .kit file onto the TclKit executable file to launch the .kit file.
For MacOS, it should be possible to launch a .kit file from the command line in a manner very similar to the Linux command line instructions above. This is due to MacOS's Unix roots. The current Password Gorilla maintainer does not have a MacOS machine, so I can not offer any further advice along these lines.
Presumably drag and drop should work on MacOS, although you may have to flag the TclKit executable to bypass the MacOS Gatekeeper subsystem. Some instructions on how to do this collected from information provided by actual MacOS users can be found here.
It may also be possible to associate a .kit file with the TclKit executable on MacOS to allow launching the .kit as if it were a normal application. As the current maintainer has no Mac machine, at best I can only recommend an internet search for details on whether this option is possible
It is possible to launch a Password Gorilla .kit file on MS Windows from the command line. The command to type is identical to the example given for Linux above. The difference is there is no 'chmod' operation on windows to mark a file as executable, instead the filename has to end in .exe.
It is also possible to drag and drop the .kit file onto the TclKit executable to launch the .kit on windows. As well, it is also possible to setup Windows file associations to associate a file ending in .kit with the TclKit executable used to launch the file. For help on setting up Windows file associations it is best to refer to an internet search for Windows specific details.