git pull origin master
npm install
git checkout -b (whatever branch)
gulp

When you're ready to push:

git add .
git commit -m "(some message)"
git push origin (whatever branch you are on)

After that, go to the branches page of the repo on Github and create a pull request. Once that's all done, let the group know that your code needs a review. Someone else will respond on Slack, review the code, and merge it when they're ready.