The ISO file you download is a data image of a disc so this isn't something you just download and run. You need to burn it to a DVD using your burning software's "Burn Image" or "Burn ISO" option.
Do NOT just drag the ISO file onto the disc and burn that as that's not how it works. You can check the burn is successful because the DVD will then show all the installation files - if you see anything else you've done it wrong.
Now you have your installation disc ready for when you build the computers. So go and download everything you can right now (i.e. both 32 and 64-bit versions and XP Mode for the crack of it) and burn your discs ready.
They don't expire until March next year.
I don't mean to be rude though, but if you're not familiar with something as commonplace as disc images and torrents, should you really be installing and using an unfinished operating system on your computer?