I think you can solve this pretty easily. If you have the ISO file, you should be able to mount it in any "live CD" version of Puppy Linux. If you can create a folder in your hard drive, and name it 'FossaPup64', then click on the folder with the ISO file, it should mount and you should be able to view all the files in the ISO without burning it to a disc. The ISO should now appear as a folder. You should be able to highlight all the files of the ISO and drag them into your new 'FossaPup64 folder'. Select the "copy" to folder option.
Actually since you already have the DVD with all the files, you likely can just drag these files from the DVD into your new folder.
If you're running a LiveCD of any of the common Puppy's, you should be able to run either the 'GrubforDos' utility or the 'FrugalPup' utility. These will be able to pick out your new folder with the OS's files (that you just dragged from the ISO).
Just look in your applications menu under 'Setup' for a program that has the word "frugal" in it. If you come to an option that says "legacy" I suggest that at first you select that as well. You can find step by step instructions for installing a frugal version of Puppy in more than one place. Jump in the water's fine.
The utility should be able to install a "frugal" version of the OS and when you reboot, the Grub menu will load and automatically run the FossaPup operating system. Without a CD or DVD.
I hope this helps.