This is for those who don't know what VASSAL is or how to use it to play TSSSF.

First of all, what is VASSAL? Well, you know how when you want to play a game with some friends, you normally all sit down around a table with things like a gameboard, some game pieces, and/or some cards? Well VASSAL is basically that table, but on a computer. It lets you play games with people online either live or via email.

Before anything else, you'll need to download and install VASSAL. Get it here.
After doing that, I recommend going through the tour that comes with VASSAL. It will run you through the basics of using VASSAL. (Though to play TSSSF, most of what you really need to know can be summed up as click, drag, and sometimes right click.)

Now that you know how to use VASSAL, let's go over how we're going to use it to play TSSSF.
1) Go download the TSSSF module here and put it somewhere you can find it.
2) Either run VASSAL and select "Open module" in the file menu and find the module you downloaded in the last step, or just double click on the module itself.
3) The new game wizard will have a few different options for playing, but for our game, select "Load a saved game" and press the Next button.
4) Press the Select button and find the log file for the game (which will be emailed to you after each turn when we begin).
5) If this is your first turn, it will ask you what side to join. Select whatever player number you were assigned and press the Finish button. If this is not your first turn, this page will not appear.
5) Use the Step Forward button to step through the previous player's turn.
6) If it is not your turn now, then you're done. Wait for the next player to take their turn.
7) If it is your turn, press "Yes" when the game prompts you to start a new logfile, or select "Begin Logfile" from the File menu and choose a save location you can find later.
8) Take your turn. You can make comments in the box at the top of the screen to do things like explaining who the changelings are imitating or making amusing comments.
9) Select "End Logfile" from the file menu.
10) Write those fics!
11) Email the logfile to all the other players.

And that's it. If you need help learning how to play, look at this thread.

3544922 Very helpful, thanks!

A few notes:

We're using TSSSF module version 1-0-3e.

Each log file starts and ends a player's turn. To see everything that's been done so far in the game you'll need to download all the files (currently just 2 of them), open the TSSSF game module in VASSAL, load each log file in order, and then use the step forward button in the program to see what's happened. You don't have to load each if you already know or don't care what's happened thus far, but before you take your turn, load the latest log file, and, like it says in J's tutorial, step through and then start a new log file when it can't be stepped through any more (reaches the end of the last player's turn). Then you can start your turn.

The game won't show a message when a player draws, so my log file, named Deal 2, will look like nothing is happening when you step through it until it asks you to create a new one. All I did was draw 4 pony cards and 3 ship cards for my turn per the game setup rules, (using the right click menu for each deck).

3590484
Thanks for adding that. It is annoying that VASSAL records draws and the movement of cards in your hand as steps without giving any indication that anything happened, but that's how it is.

(Also, you snuck my real name in there.)

3590753 Fixed. Thanks for letting me know. Glad I could contribute.

Something else to keep in mind:

On my computer, using Windows 8.1 (and maybe on other systems too), if I try to restart VASSAL, it doesn't seem to like to cooperate. The simplest option is to reboot the PC to get it to restart properly. The quickest option is to use Ctrl+Shift+Esc and stop all processes named "Java(TM) Platform SE binary" then click the VASSAL icon.

This is useful if you don't exit the program with the menu, but instead just close the windows. For some reason it keeps running in the background if I do that on my PC.