I'm in the mood!
find / -name fileName > found.whatever 2> /dev/null
to find it as a normal user. If as root, cut the 2> /dev/null
It will put everything found in the found.wahtever file in your home directory ... if you are there ofcourse. If not, use ...> $HOME/~found.whatever.
And yes, use man pages, they are your best friend!