Whilst Macs with a Superdrive continue to be able to burn video DVDs, the software for so doing, iDVD, is no longer included in the iLife bundle that came with OS 10.7 Lion and beyond. And iDVD is no longer included in the iLife 11 from the online Apple Store: http://www.apple.com/ilife/. As there is no satisfactory substitute for iDVD, your only solution is to look on Amazon or eBay and try to get an older version that includes iDVD 7, i.e. iLife version 9 onwards. You should also do this if you plan to buy a new Mac anytime soon, as stocks of iLife that include iDVD will not be available for ever.
(The vastly more expensive FCPX can burn a DVD without iDVD or DVD Studio Pro involvement, but lack the themes etc of iDVD. Also, of course, there is Roxio Toast, which is the best software for burning anything but again does not offer the flexibility of iDVD.)
It is worth noting that the version of iDVD 7 included with iLife 11 only includes themes from iDVD 5-7. If you want all the older themes you should buy iLife 9, which has the same version of iDVD 7 but with all the themes, which none of the iDVD 7 updaters available from Apple Downloads include.
Currently the only certain way to get all themes is to start with the iLife 09 disc:
https://discussions.apple.com/content/attachment/207514040
This shows the iDVD contents in the iLife 09 disc via Pacifist:
https://discussions.apple.com/content/attachment/207480040
You then can upgrade from iDVD 7.0.3 to iDVD 7.1.2 via the updaters at the Apple Downloads webpage.
But even though you can still buy iLife 9 or 11 that includes iDVD 7 from Amazon, Apple now make it difficult to install:
When you try to install iDVD you may see a notice come up on the screen stating that the 'Authorisation Licence' had expired on 25 March 2012, because Apple have withdrawn the license to it can no longer be used.
In other words Apple have declared iDVD as redundant and have made it difficult to install, but there is a workaround:
If you get an invalid certificate message just set your Mac's clock to sometime before early 2011 and run the installer. After installing iDVD reset the time back to the correct time on your Mac.
You may be to use able to use the installer even without setting back the date. Just click on the Continue button and it should work as expected, but for some it will not continue unless the date is set back.