I heard lemon juice is good for healing acne scars, I have some lemon juice how do I use it on my skin?

Had an acne promblem last year and used tablet treatment to get rid of the acne. I know have acne marks and found out about how lemon juice helps. But I never found out how to use it - am I meant to rum into my skin, or put it on and leave it there? Or anything else?
Thanks everyone :)
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