I'll assume we're starting from nothing, so the first thing we'll need to do is clone the repo … but where to put it? I like to organize files on my local machine in a way that's similar to how GitHub does it. Locally I'll put everything in a "Sites" folder in my home directory. The short hand way of refering to this in Terminal is ~/Sites/ (~/ is an alias for /Users/<your user name>/), so the full path to your sites folder is /Users/<your user name>/Sites/.
To keep with the theme of "local machine organized like GitHub", we'll start by making a directory for the organization or owner of the repo we're going to clone. This is the first part of a GitHub URL which have the form of https://github.com/<organization or owner>/<repo name>, so:
# mkdir is short for "make directory"