Yeah, depending on your current OS you can use rawrite or rawritexp (both programs can be found on the mirrors) to create a bootdisk. Just use the bare.i one to begin with, it seems to work fine in most instances. Then get the rootdisks install.1 and install.2, and use those as prompted (the installation will tell you when to put them in). After that it's Slackware 9.0 ISO image CD time, which the installation should pick up on automatically.
Now I know it's more than possible your burned CD will simply be bootable, and you won't need any of these boot and root disks, but I would suggest making them anyway, so you can continue with your installation even if you end up *not* being able to boot from the burned CD.
for the rawrite programs and bare.i
for install.1 and install.2 (also has the rawriteprograms)
for the ISO image to be burned on your CD.