Question about XDM

[Antoine Kallab]

Hello everybody,
I'm new to BSD, so please bear with me if I ask a dumb question. Thanks!
---
I am trying to set up XDM. I want it to drop me in to a minimal TWM session
after I log in. Right now, it just flashes the screen and puts me back at
the login window.
>From what I read in the handbook, there are a few configuration files in
/usr/local/lib/X11/xdm that I need to change to get it to sing and dance in
the way I want it to.
If I remember correctly, it was Xsession that controlled what happened
after a user logs in.
Right now it is just an if/then loop that looks like it runs
/usr/local/bin/xsm. Is that whole thing necessary? Can't I just tell it to
run TWM?
And if that loop is necessary, where would I add my bit for starting TWM?
Google has been ZERO help.

Many thanks in advance.