Linux real time patch question

I am trying to get the real time patch installed on a fresh RedHat 5.2
system. I did this successfully a couple of months ago but my hard disk
crashed. I have the patch untarred and the kernel sources and headers
installed. When I get to the place where you cd/usr/src/linux and run the
script "patch -p1 < ../kernel_patch" I get a file not found error. Where
does the patch script come from?

Thanks,
Terry