ffmpeg – Can someone teach me about downloading DRM content?

There is some videos that I would like to download that are DRM protected. I tried using StreamFab for the first time yesterday and it told me that the encryption used in the video was unknown or something like that.

I have read that you have to get some keys and then unencrypt something. But I have tried researching it many times and I have never found someone throughly explain all the process. Most of the videos that I need are on the -N-B-A- site.

Could someone explain to me the process of how to do that?