I logged on to FVWM, opened an xterm, typed "nm-applet", opened another xterm, typed "firefox", and now I am posting this running under FVWM!

I still would like a system tray application, it seems convenient.

I also wonder if there is some kind of way to have a script run on startup, that can start the system tray, nm-applet, GKrellM, etc.

It's "stalone", stalonetray. This is the home page,

http://stalonetray.sourceforge.net/

But most likely, it's between the standard set of packages of your distro, so try your package manager first. There are several more if you can't find that on your package manager: wmsystray, trayer, docker or peksystray.

That's "StartFunction", you can add everything you want in there. Open your ~/.fvwm/config file in a text editor and start adding things.

And so on. You should really read the fvwm man page. Everything is in there

"yum install stalonetray" worked. it is showing a little grey box with the nm-applet icon in it.

Yes. You probably want to research into FvwmButtons and FvwmIconMan next (both have a proper man page). FvwmIconMan is a task manager, it can serve as a taskbar. You can use FvwmButtons as a container to embed (swallow in fvwm terminology) FvwmIconMan and stalonetray, kind of emulating the typical desktop panel if that's what you want.

I have no idea how to set it up. The main problem is that everywhere the keep mensioning a ".fvwm2rc" file in yout home dir, but in mine, I have a .fvwm directory with many, many config files in it.

Historically, fvwm has been configured in a number of places. They all are listed in the fvwm man page

Right, now, the preferred place is $HOME/.fvwm/config. The name of the file is irrelevant, except to determine the order for the lookup (only the first config file that is found will be used, a thing that you need to keep in mind).

Second, you are not supposed to have an ~/.fvwm/config file, you are the one to create it. Fvwm has never been -and probably will never be- a wm that can be configured using point & click. To access its full potential you need to read man pages and be prepared to write the config yourself.

Alternatively, you can use either fvwm-themes or fvwm-crystal, which are nothing but pre-made complex configurations for fvwm (I know very little about these).

I have no idea what do you have in your ~/.fvwm/ directory, it might be some leftover of some experiment that you don't remember, maybe you downloaded some config from another user or something. Or maybe it's something from fvwm-themes or fvwm-crystal. I have no way to know how did that came to be there.

A vanilla fvwm screen looks like a grey background, and the only thing that you can do on it is to click on the root window to bring up a menu which has 6 options.

The rest, needs to be configured by you using ~/.fvwm/config. This guide perfectly guides you though the process of setting up most basic elements:

http://www.zensites.net/fvwm/guide/index.html

Also, you should really start using the fvwm man page.

You can try this as a starting point:

Note that, the font is the one I use, you might need to change it, it won't even work (default to "fixed") if you don't have DejaVu installed. Second: you might need to adapt the stalonetray command to whatever you use to launch stalonetray. I don't have it installed so I am not sure.

This simple configuration should show a bar on the bottom of your screen with a button to reach the default fvwm menu, a task bar, a desktop pager and the system tray on the bottom right. Copy this text, and paste it as a whole in ~/.fvwm/config, if that file already exist make sure you delete it before or move it elsewhere (I'd just remove everything into ~/.fvwm/ if you plan to create your own config.

What's the difference between "deleting", "destroying", and "closing" a window? Which one should I use to exit a program, like the close button in Windows and Metacity?

Normally you want "Close".

I haven't looked into it, but I think that it just uses the WM_DELETE_WINDOW protocol to ask a window to gracefully close. If the application doesn't understand it then the window is Deleted as with the Delete command. However a window could understand but ignore Close and it would not be Deleted, which is why Delete exists. You usually don't need Delete unless you are using old or very odd software.

About Destroy, in my experience it's mostly like using "kill -SIGKILL" or xkill. It will force the application to close by any possible means, so it's "the strongest" of the family.

Some people, when binding the mouse to the titlebars buttons, bind each button of the mouse to one of these three commands, so you can have the three using a single titlebar button.