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.
(..) fuII, pouting Iips... a white bIouse, green jacket... and a name tag. You reaIIy narrowed it down. Too bad she's aIready taken. HeIIo there, may I be of assistance? StanIey Ipkiss? Hi! I'm Peggy Brandt from the Tribune. I canceIed my subscription because they kept steaIing-- ReaIIy? About what? (..)1994 The Mask