What's the way to set openbox or icewm as default desktop from any display manager?

English Install/Boot/Login
1

What’s the way to set openbox or icewm as default desktop from any display manager?

It’s kdm installed now.
And automatic login is enabled from yast2.

2

Doesn’t autologin start the last session used ?

3

In /etc/sysconfig/windowmanager edit the line starting with ‘DEFAULT_WM=’.