Beauty And The Beast On Blu Ray

beauty and the beast on blu ray
Need a backup, please teach me how?

Recently i have purchased a new blu-ray Beauty and the Beast, how to create a digital copy so that i can play it on my computer?

no no, handbrake never work for blu-ray.
you need a Blu-ray ripper.

You can read the following tutorial:
Backup Blu-ray in MKV format, keeping High Quality and all BD features – by converting Blu-ray to MKV video, on one hand, you preserve the entire video/audio/subtitle tracks into one single MKV container video. On the other hand, it is more convenience for you to archive you videos (contained in one file is better than hold in multi folders). After backup your Blu ray to MKV video file, you can avoid BD physical damage or loss.
Find original source at: http://www.winxdvd.com/resource/rip-blu-ray-to-mkv.htm