The recommended way is to use the git remote add origin command ... go to your existing project and copy all the files, with the exception of the hidden .git folder, into the cloned repository. Then ...

If the existing project does not already use Git, issue a git init command in the root folder. After the repository is initialized, add all of the project files to the Git index and perform a commit: ...

Jack Wallen shows you how to add a GitHub shortcut to a Jira project so you can view ... is also connected to the GitHub repository and then paste/run the command. The same thing holds with ...