git checkout -b your-new-branch
git add <files>
git commit -m <message>
First, checkout your new branch.
Then add all the files you want to commit to staging.
Lastly, commit all the files you just added.
You might want to do a git push origin your-new-branch afterward so your changes show up on the remote.
git branch branch_name <commit-hash>
git checkout branch_name
git push --set-upstream origin branch_name
git branch branchname <sha1-of-commit>