There are two possible ways to take care of this.
Debian is all about free open source software, it does not include firmware for proprietary network devices in a default installation, you may be able to add a non-free repository in the /etc/apt/source.list where you can select the firmware for the device to be installed in a simple manner through synaptic or via apt from command line, but I have no such device therefore cannot say for sure if it's that simple.
My Debian Lenny comes with kernel 2.6.26, according to this article ---> http://wiki.debian.org/iwlagn
, you need a newer kernel (2.6.28 or higher) which will have the driver included. Then you would unpack the ucode package (firmware) you have or the one recommended in the article link and move all files ending in .fw to the /lib/firmware directory to enable the device.
I suggest following the instructions in that article for Lenny to add neccessary repositories to your /etc/apt/sources.list so you can upgrade your kernel to at least 2.6.28 (2.6.29 according to the article) which will have the driver (module), then install the firmware to get it up. I personally would try the ucode package you have rather than the one recommended first as it appears to be a newer version, if it don't work, go with what the article suggests. Or just follow the entire proceedure recommended in the article.
Step #3 tells you to add this line to the /etc/apt/source.list ---> deb http://kernel-archive.buildserver.net/debian-kernel
Find the source package for the driver and compile it to work with the current running kernel you have. Then unpack and install the firmware in same place as previously suggested.