Best way is to go to the site that Pete posted.
Download the ISO using the tool and then use Rufus to create a bootable drive with the ISO you just downloaded.
(I know the tool "can" create a bootable drive, but it has failed to me in the past, not without wasting precious hours, so I recommend you download it and then use Rufus.)
Note: you'll need another computer to do what I said above.
Note 2: I would recommend that you reset BIOS settings to default in case the previous owner changed something you don't want changed.