First time rails install, help with gems/rake

Hello all,
    I just did a first time ruby enterprise edition, installed some gems,
and now I'm trying to do a ' sudo ./rake gems:install' and getting a:
rake aborted!
No Rakefile found

error. Firstly, what directory should I be doing this from?

You should be doing it from the root directory of a Rails app (in
other words, the one with app/, config/, db/, log/, lib/, vendor/
etc).

If you're someplace where you can do ./rake and have it work, you're
*definitely* in the wrong place.

--Matt Jones