First booting it requires this bit set at boot. During install you will need to enter it at the loader prompt.
Then when finishing the install you will want to add that to '/boot/loader.conf' before exiting and rebooting.
That all is also handy to add as well. The mouse will load up as a UHID device otherwise once devd starts if you let it. Also as / is not mounted yet, unless you load the FW now, the kernel won't be able to load it automatically. The last two are optional.
Just do your standard X stuff and then change the driver to this...
Section "Device" Identifier "Card0"
Option "Rotate" "cw"
Option "NoAccel" "True"
The framebuffer driver actually works rather well. Although it will load up corrupt every other time, so you may need to kill X if you restart it.
Sadly FreeBSD as no equivalent of fbcon=rotate:1 .