You have been given a clone of the git-mastery/gm-shapes repo.
Another developer Alice’s has created a remote copy of this repo at https://github.com/git-mastery/gm-shapes-alice which seems to have an additional commit in the main branch.
Add that repo as a remote titled alice-upstream, and bring over Alice’s additional commit to your repo.
Alice’s friend Bob has copied Alice’s repo to https://github.com/git-mastery/gm-shapes-bob, and added one more commit.
Add that repo as another remote titled bob-remote, and fetch (not pull or merge) his new commit to your repo.