Git repository

You should move this question to the Continuous Integration and Source Control section since your question is about git version control, not Interface Builder.

When you ask "after it has been created", do you mean you want to place an existing Xcode project in a git repository? If so, the answer is Yes. In Xcode choose Source Control > Create Working Copy. You can also place a project under version control from the Terminal by navigating to your project folder and running the git init command.