Post Upgrade Help for Dummies - composer.phar &

[chewiesw]

I have upgraded from 1.4 to 1.6.2 and everything seem to be working.  However I have two error messages I need help with.

I have been told to run run `php composer.phar install --no-dev` for the life of me I can't figure out how to do this.  I always get  "Could not open input file: composer.phar "

Secondly when I run the installer

GuzzleHttp\Client:  NOT OK(Failed to load class GuzzleHttp\Client from github.com/guzzle/guzzle)

help please