Microsoft has realesed the ISO file for windows 10 and you can get them here.

http://windows.microsoft.com/en-us/windows/preview-iso



NB-The easiest way to convert an ISO file to a DVD is to use Windows Disc Image Burner.

Remember, trying out an early build like this can be risky. That's why we recommend that you don't install the preview on your primary home or business PC. Unexpected PC crashes could damage or even delete your files, so you should back up everything.

If you want to stop using Windows Technical Preview and return to your previous version of Windows, you'll need to reinstall your previous version from the recovery or installation media that came with your PC—typically a DVD. If you don't have recovery media, you might be able to create recovery media from a recovery partition on your PC using software provided by your PC manufacturer. You'll need to do this before you upgrade. Check the support section of your PC manufacturer's website for more info.

After you install Windows Technical Preview, you won’t be able to use the recovery partition on your PC to go back to your previous version of Windows.