Clarify installation instructions

[amandapouget]

For some reason, installation did not work for me. I:

• downloaded the repo
• moved it out of downloads to Desktop
• two-finger-clicked "get info" and then copied the "Where" (path) of zshrc.sh
• $ atom ~/.zshrc

Saw this:
export PATH="$PATH:$HOME/.rvm/bin" # Add RVM to PATH for scripting

Changed to:
export PATH="$PATH:$HOME/.rvm/bin" # Add RVM to PATH for scripting
source /Users/amandasimon/Desktop/zsh-git-prompt-master
PROMPT='%B%m%~%b$(git_super_status) %# '

Restarted my terminal and cd'd into a git directory but saw no changes.

What am I doing wrong?