You need to separate out the different things.
One, you want to write an addiction memoir. Good for you. It will probably be personally helpful and cathartic, and you definitely should.
Two, you’ve never written anything before, don’t know anything about writing, and don’t seem to read widely outside specific memoirs that you feel reflect your own experience. Not a problem, either, if you’re just writing for you, as a private cathartic act. There are courses and books on memoir/life-writing.
But, three — all these things become an issue if you want/expect to publish your memoir. Publishing is an industry, and you will generally need to be taken on by an agent first, after you have written your book, who will then submit it to editors, and both agent and editor will only accept your book if they think it will sell. Meaning it needs a USP, strong writing, originality. Which are entirely different qualities to you wanting to get something down for your own sake, or to help others.
For instance, this was a big success a few years back — Amy Liptrot’s The Outrun:
https://www.theguardian.com/books/2016/jan/22/the-outrun-amy-liptrot-review-by-will-self
You can see why an agent and editor took it on, why it won prizes and there’s a Saoirse Ronan film being made of it. The author grew up on an Orkney croft with a ‘good lifer’ bipolar father and a born again Christian mother, became an alcoholic drug addict during a chaotic ten years in London and returned to Orkney newly sober to work in conservation. It’s nature writing as well as an addiction memoir, with beautiful, brutal settings and a vivid backstory. Her ‘now’ in recovery is as interesting as her backstory. Also, the author is an excellent writer.
See also Cheryl Strayed’s Wild.
Basically, I think you need to distinguish your desire to write this and your motivation to do so ( and I think that a book you intend mostly for your family to read would need to be quite different to one intended to help addicts in recovery) from the marketing/saleability requirements you would need to think about if you wanted to try to publish this via the traditional route.