Clone an existing repo

git clone ##MY REPO##

Create a new branch

git checkout master # we want the branch starting from master
git branch feature
git checkout feature

Push a commit in the new branch

 git add --all # or better, the new files one by one
 git commit
 git push origin feature

Extra github trick

Quickely edit the repository using VSCode online by changing github.com to github.dev in the repository link.