Install on Ubuntu/Debian:

sudo apt-get install git-core

Install on CentOS/Fedora/RHEL:

yum install git-core

git config --global user.name "Your Name"
git config --global user.email you@example.com
git config --list

Inside your project folder

git init
git status
git add .
git commit -am "Initial Version"

And then when you make a change do:

git add .
git commit -am "The Change You Made"

To do it remotely, and push it to a repository on GitHub:

git remote add origin https://github.com/YourUserName/YourRepository.git
git pull origin master
git push origin master

And then when you make a change do:

git add .
git commit -am "The Change You Made"
git push origin master