1. Fork at github.com
2. Clone it locally
git clone git@github.com:<your name>/<repo name>.git
3. Configure username and email address
git config user.name 'Yogesh Sharma'
git config user.email 'Yogesh.Sharma@xyz.com'
4. Add upstream
git remote add upstream git@github.com:<remote name>/<repo name>`.git
5. Fetch & Merge upstream
git fetch upstream
git merge upstream/master
6. Commit & Push
git commit
git push
7. On github.com make a pull request
8. After PR is merged pull upstream and rebase
git fetch upstream
git rebase upstream/master
git push origin master --force
or
git fetch upstream
git checkout master
git reset --hard upstream/master
git push origin master --force