$ git remote -v
# List the current remotes
origin  https://github.com/user/repo.git (fetch)
origin  https://github.com/user/repo.git (push)

$ git remote add upstream https://github.com/otheruser/repo.git
# Set a new remote

$ git remote -v
# Verify new remote
origin    https://github.com/user/repo.git (fetch)
origin    https://github.com/user/repo.git (push)
upstream  https://github.com/otheruser/repo.git (fetch)
upstream  https://github.com/otheruser/repo.git (push)