I am brand new, just registered. The funny thing to me is that as a beginner I am searching for a "where and how to get into editing". Do I "log in"? do I access via the ftp?
In order to begin editing, you first need to have a copy of the Zen Cart distro located on your PC.

Check here for Text editors and other useful tools for working with Zen Cart
http://www.zen-cart.com/wiki/index.php/Useful_Tools

Once you've edited and saved your files you can upload them to your server using an FTP client.