Well, the release notes actually don't go through the step by step, but rather point to a wiki page that does:
http://fedoraproject.org/wiki/Docs/CustomKernel
This goes through all the steps needed to build a custom kernel, including getting the source installed on your local system. Of course, if you just need the source, you don't need to proceed with the build.
Before that, however, check that you need the full kernel sources and not just the kernel headers. A quick check of the ndiswrapper install info (
http://ndiswrapper.sourceforge.net/j...,installation/) suggests you only need the kernel headers for this, which is much easier:
yum install kernel-headers
should work here.