If you've already got a DVD writer/rewriter (either built into your computer or as a standalone unit), then this is the
software that you need:
https://www.ashampoo.com/uk/gbp/pin/7110/burning-software/burning-studio-free
If you're actually seeking a DVD writer/rewriter, you're unlikely to get one for free unless you're very lucky on Freecycle or Freegle. Otherwise you'll have to check out eBay, or similar, to find a cheap external one. (They start from around a tenner) NB: If you're going to be playing the DVDs you make on a TV, rather than on a computer, take care to check what formats your DVD player accepts. Some accept both DVD-RW discs and DVD+RW one, whereas others might only recognise one of those formats. You need a DVD-writer/rewriter which burns to the same format.
Remember too that commercial DVDs are usually copy-protected, so you can't copy them directly; you have to use software like Handbrake to extract all the data and then use that data to burn a new DVD, which can take several hours just to copy one disc.