How can I set up an existing site from Pantheon on my computer?
Uploading your key is the first step towards cloning your repository because this gives you access. The next step is to grab the git repository address from your site's dashboard. This is located in the "Connection Info" dropdown menu on the upper righthand side, or in the "Connection Mode" bar above your commit log. The info button provides the git commands you'll need to get started. Please note that you'll need to be in the Git mode in order to push your local commits to the Pantheon repository.