My guess is that you open up Split, then select a file.  It'll then probably prompt you with some options such as Part Size or something similar.  It'll then take a file and split into smaller chunks (say, 1.4MB chunks so you can put a large file onto multiple floppies.)

Then you use the Join File Splitter application to join all those chunks back together to form the original file.

You'll want to copy Split and Join to your hard drive and not run them off the floppies.

Stuffit Deluxe or Compact Pro can do something similar (and perhaps better) because it can make it not only split into several pieces, but also self-extracting so you don't have to worry about joining the file back together.