Add ssh key for GitHub

ssh-keygen -t rsa -C <email here>

sudo apt-get install xclip

xlip -sel clip < ~/.ssh/id_rsa.pub

Now just add the key through the github interface
To make the repo push over ssh

git remote rm origin
git remote add origin git@github.com:your_username/your_project.git

To add the upstream repo and synch with it

git remote add upstream https://github.com/upstream_name/project.git
git fetch upstream
git checkout master
git pull --rebase upstream master
https://help.github.com/articles/generating-ssh-keys