Q regarding live CD creation for 16.04

Hi all,
I'm technically so-so. I have an old 64bit vista system, and 2 old XP systems. I'm interested in putting Ubuntu 16.04 LTS on them. I have d/l'd the .iso images for the 32 bit and the 64bit systems. I selected 'desktop' for both images. I have tried buing the iso image several times for both, they bu correctly, but I caot make them bootable. I've done so much looking and reading on the UBuntu site that I've now confused myself rather well.

I have used an .iso viewer to look at each and, from what I could find on the site, - an image that showed a number of files such as autorun, start, etc, these images I d/l'd don't seem to be complete for a (windows??) boot as they aren't in my .iso's. I have followed a number of the instructions for buing a bootable dvd, but it seems the .iso 's I d/l'd do not contain this info.

As I mentioned, I'm now totally confused and at a dead-end. I'd like to get bootable (after .iso bu) images for both the 32 and 64 bit packages, but I just don't know how or where to find them.

Will someone please help out an old f*rt trying so hard.

Thanks

Ken