How does the བར་དོ་ཐོས་གྲོལ (Bardo Thodol) "Tibetan Book of the Dead" fit in with the Kangyur and Tengyur

_I am looking for a public domain copy of the Tibetan book of the dead (in original Tibetan script, not a translation) online in text format (i.e. not a PDF). This lead me to the main question..._ My question is, I have seen the large volumes of the [Kangyur](https://en.wikipedia.org/wiki/Kangyur) and [Tengyur](https://en.wikipedia.org/wiki/Tengyur) , but then independently there is this book [Bardo Thodol](https://en.wikipedia.org/wiki/Bardo_Thodol) , _The Tibetan Book of the Dead_. They say it is from [Nyingma](https://en.wikipedia.org/wiki/Nyingma) literature. Being a novice, I am trying to understand the relation between Nyingma and Kangyur/Tengyur. And thus how the Tibetan Book of the Dead fits in. Wondering if one could outline the relations between them.