You will need a minimum 3 floppy disk, and some means of writing images to them.
Then pick a kernel image from the slackware cd and put that on the first disc.
After that put the rootdisk (install.1 and install.2) on the next two disks, i think these are on cd2, or u can find them on the slackware site under the rootdisks directory.
If your cdrom is on a pcmcia adpator you may need the pcmcia.dsk image (also found in the rootdisks directory)