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 and Tengyur, but then independently there is this book Bardo Thodol, The Tibetan Book of the Dead. They say it is from 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.
The Bardo Thodol is an extract from the Guhyagarbha tantra, which is the most important tantra in the Mahayoga class, and the most studied tantra within the Nyingma school. The Guhyagarbha is certainly in the Kangyur.