How can I help someone who knows has ADHD but doesn't want to get professional help but doesn't mind me helping them out?

So my partner and I had a discussion recently and we both have discovered that he might have ADHD. He looked up the symptoms and he said majority of them he can relate to them and one of the things that he deals with is his mind racing everyday. He said he probably won't get professional help but will do some research him self and doesn't mind my help helping him out.

How can I help someone who knows has ADHD but doesn't want to get professional help but doesn't mind me helping them out?
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