If you have a local repository already connected to a remote repository (Github) and you want to update the connection to a different remote repository.
Verify the repo it is already connected to that you want to change
git remote -v
Grab the URL from the new repo you want to connect to
git remote set-url origin git@github:USERNAME/REPO.git
Example
git remote set-url origin git@github:darnocer/README-Generator.git
If you run into this error:
> error: No such remote 'origin'
Connect to the repo first:
git remote add origin git@github:USERNAME/REPO.git
If the new remote repo is empty, overwrite it with your local repo contents:
git push -f origin master