GitHub.com is a hosted source control repository running the very popular Git software. It allows users to more easily setup and manager remote repositories. When people save their changes back to the repository, a "service hook" is activated automatically which sends information about the activity to third parties.
Snowy Evening accepts these connections and saves information about them to an issue any time you mention an issue in the commit message.
Log in to your account on GitHub.com and access the primary project page of the project(s) you wish to add service hooks for. You should have a similar project name in Snowy Evening.
Click on the "admin" button at the top of your project page
Select the "Service Hooks" link on the left-hand navigation bar.
Then select the "SnowyEvening" link...
...and you will see fields for your project ID and API Key.
Enter the project id and API Key as they appear on your "Edit Project" screen.
When composing your commit messages, refer to the bugs for the project just as you would for issue comments and once you push to origin, those commit messages will attach to the issue history.