[Q] Kindle Fire HD 8.5.1 Root?

So I recently got this Kindle Fire HD 8.9' and wanted to root it for my parents. I'm having trouble finding a definitive guide to rooting it as I'm not that experienced in rooting. I've rooted my other devices, but only with the help of a video+text tutorial. I was wondering is there any good text guide I can follow to root this tablet? Thank you for any help.

P.S. I've seen the threads on how to root, am having trouble following them that's all

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