If you still have iDVD in your Applications folder, here is a step-by-step:
1. Create a project in iMovie 10.0.1
2. Go to File>Share>File... and for Size choose Large 540P (960 x 540) and click Next
3. Choose a location on the hard drive to save the file to.
4. Wait for the blue circle activity indicator to finish.
5. In Finder, verify that iMovie created an MP4 file in the location specified in step 3.
6. Open iDVD and click "Create New Project."
7. Give the project a name and save it to your hard drive.
8. Drag the file you created earlier from the Finder into your iDVD project window.
(or go to File>Import>Video... and choose your video there)
9. Make any adjustments to drop zones, etc.
10. Click the burn button.
11. Insert a DVD and let it do its thing.
If you don't still have iDVD, look on the Mac App Store for DVD burning software and use it for steps 6-11.