Can't Find To Change Preference

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I am reading comments on a health issue & ran into this: 'this post contains content of mature nature. You have selected to not view content of mature nature. If you would like to view this post, you must first change your preferences to allow mature content'. I cannot find anything in 'preferences' to change this. I'm new at using this site & am just learning my way around. Could someone please help me out? Thank you. Marlene