We value Open Source and make a point to release all our plugins on GitHub under a BSD License.
Inside Atom, navigate to Preferences (or Settings) → Install and search for wakatime.
Click the Install button.
Click the Settings button inside the wakatime package.
Enter your API Key.
Type some code, then visit your WakaTime Dashboard to see your stats!
Alternatively, you can install WakaTime from command line with apm install wakatime.