He wrote the story with his friend's 'assistance'. = He wrote the story 'with the assistance of' his friend. [=his friend helped him to write the story]
Our family had to 'go on public assistance' [=receive money from the government] when my parents lost their jobs.
Nobody 'came to her assistance' [=nobody helped her] when her car broke down.
(..) - You'll have to turn around. - He'll tell you. l just... Mr Hockley and Mrs DeWitt Bukater... ..continue to be appreciative of your assistance. They asked me to give you this in gratitude. l don't want your money... You hold a third-class ticket. Your presence here is no longer appropriate. (..)1997 Titanic
(..) The best l've seen, ma'am. Hardly any rats. (laughter) Mr Dawson is joining us from the third class. He was of some assistance to my fianc'e last night. Mr Dawson is quite a fine artist. He was kind enough to show me some of his work today. Rose and l differ somewhat (..)1997 Titanic