My new Mac didn’t have iDVD.
Then how to export iMovie project to DVD?
You could also share to iTunes, add the movie to a playlist, and then go to File>Burn Playlist to disc. However, iTunes burns movies as .m4v file which your DVD player may not be able to read.
Additionally, you can share to iTunes and put resulting movie on an iDevice to view and share it that way.
If you have old Mac OS X installation disk,then from it you can install iDVD.
If you want free solution,then you can use Burn software.
Easily Burn Movies to a DVD without Apple's iDVD
Note :- You'll need to export only VIDEO files and not PROJECT files for Burn to work with.
Else,you can also use a commercial third party product called Roxio Toast.
perhaps you need iLife
How to create a video-DVD? (Macs without iDVD)