From the page you linked, "The latest stable version of the Linux kernel is: 18.104.22.168"
There is no kernel image from The Linux Kernel Archives; that is the kernel source.
If you compile your own kernel on another machine, you can put it on media to select
during the Slackware install. Otherwise, you need to install with Slack's default 2.4.31
kernel and then install your custom kernel after the OS has been installed. If you don't
know how to rebuild a kernel, I'd suggest this Kernel Rebuild Guide
There is a 2.6.13 kernel on the Slackware-10.2 CDs you can use, however, it's going
to be different than the default one. You'll need to carefully
read the RELEASE_NOTES
file if you want to use that kernel.