to use your chosen window manager, choose it in your display manager. e.g. in gdm, there is a gear icon on the bottom right which displays a menu of window managers when clicked.
alternative display managers available as swupd bundles are sddm and lightdm.
you can start the xorg based window manager of your choice directly from the tty with startx command. to do this, put exec $WINDOW_MANAGER (where $WINDOW_MANAGER is the wm of your choice) in your xinitrc (/etc/X11/xinit/xinitrc for system wide, ~/.xinitrc for local user). you must also remove the desktop-autostart bundle so that gdm should not automatically start.