simple documentation question (adding a disk)

[Benjamin P. Keating]

The 'Adding a Disk' page in the Handbook explains how to add disks to
the system via /stand/sysinstall

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/disks-adding.html

Im running FreeBSD 5.2.1 and followed the directions on the above link
but fdisk gave me a heads up when trying to commit my changes (w):

%<---------------------------
WARNING:This should only be used when modifying an EXISTING
installation.  If you are installing FreeBSD for the first time
then you should simply type Q when you're finished here and your 
changes will be committed in one batch automatically at the end of
these questions.  If you're adding a disk, you should NOT write
from this screen, you should do it from the label editor. 
>%---------------------------

Im just curious, is the documentation out of date or the sysinstall >
configure > fdisk? Doing it via the 'label editor', im assuming mean
bsdlabel, correct? Then this confuses me because dmesg reports i have
a (for example)  ad4 device (/dev/ lists no other ad4 slices). So i do
a:

%<---------------------------
bigbang:admin> sudo bsdlabel -e ad4
bsdlabel: /dev/ad4: no valid label found
>%---------------------------

Would anyone be so kind to share with me there notes on adding a new
disk to a system? sysinstall > congiure > fdisk seems to work but that
warning confuses me.

Thanks.
- bpk