It's been some time since I've done it, I mostly just watch nowadays. To
install on a B&W G3 you need to put the netbsd-GENERIC_MD file on your HFS
partition, your zip in this case and boot it. Once it is booted you can
then mount your CD and install from there, you can also configure your
network and install from it if you would like.  Check the mailing list
archives, I once posted a fairly long description of this. (There are some
spelling errors, sorry.)

Good luck.

Rob