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.
(..) around so much death and that your friend had to see this. The cranial-facial work is tricky, but I'll do what I can before you arrive. Of course I'll wait for your assistance before I hoist. I think that's a good idea. And again, Federico, I am so sorry about what happened. (..)2003 TvShow: Six Feet Under Title: Making Love Work Season: 3 Episode 6