Here's a good link on Fedora Core 6:
http://www.fedorafaq.org/
Replace your yum configuration with the one suggested there, then at the command line type:
yum -y --enablerepo=freshrpms install dkms-ipw3945 ipw3945d ipw3945-firmware
I believe you might have to also do a 'modprobe ipw3945'. Your wireless card should be good to go after that.