NOTE --since this was originally posted, ATOM has been acquired by others and morphed into VScode. ATOM is no longer supported.
An overview of the steps you need to take to get Arduino projects running in Atom. This is a hybrid solution that uses the External Editor functions of the Arduino IDE. It does NOT cover pathways for Arduino uploads in Atom. Various solutions to this problem exist but I have found unstable are overly-elaborate. I find this a good compromise in my personal workflow. YMMV.
You can find the Atom download info and the Atom packages required in the Software Installs post.
00:00 intro
00:40 Arduino IDE
01:45 preferences external editor
02:40 Arduino code in Atom