If you have not set your username, IntelliJ IDEA will prompt you to specify it when you first attempt to commit changes.
Git needs to know your username to associate commits with an identity. This involves committing them locally to record the snapshot of your repository to the project history, and then pushing them to the remote repository so that they become available to others. After you've added new files to the Git repository, or modified files that are already under Git version control, and you are happy with their current state, you can share the results of your work.
