Selecting a Theme
Robby's theme is the default one. It's not the fanciest one. It's not the simplest one. It's just the right one (for him).
Once you find a theme that you'd like to use, you will need to edit the ~/.zshrc file. You'll see an environment variable (all caps) in there that looks like:
ZSH_THEME="robbyrussell"
To use a different theme, simply change the value to match the name of your desired theme. For example:
ZSH_THEME="agnoster" # (this is one of the fancy ones)
# see
https://github.com/ohmyzsh/ohmyzsh/wiki/Themes#agnosterNote: many themes require installing the Powerline Fonts in order to render properly.