It is quite simple to download videos from YouTube and use it for personal use only. You are not allowed to sell any videos on DVD due to copyright violation rules but for personal consumption it is fine.
The following are the steps:
(1) Open YouTube website and search for the videos you want to download. Copy the address link of the YouTube videos you want to download. (Left click on the address bar of the window and then right click to bring out the menu, choose "Copy" from the menu)
(2) Go to http://keepvid.com/.
(3) Right click on the box beside download and paste your YouTube video link. Click "Download".
(4) Now a list of available videos will be displayed in various format. Choose the "Download MP4" - 480p, or "Download MP4" - 720p only. Do not choose other ones because they either contains only video with no sound or audio with no video.
(5) If you haven't downloaded the free DVD burner software, you can download it here, "Express Burn Free". (No virus and no malicious adware on http://download.cnet.com)
(6) Now using the Express Burn Free software you can burn those downloaded software onto a blank DVD.