1. cd to your forlder

cd /yourfolder/

2. check git information

git checkout -b branch_name # use -b to add a new branch
git branch # check branch info under this repo

switch branch

git checkout branch_name

3. update the file

git add file_name # update a file
git add . # update a folder

4. commit the update

git commit -m "comment_here"

5. push the update

git push -u origin branch_name