To add a new heroku app simply call:

heroku create

You now should have a heroku remote. Check with:

$ git remote -v

You can set heroku to be the default remote for push/free:

$ git config branch.master.remote heroku

You can deploy with:

$ git push heroku master

If you encounter the error Permission denied (publickey). while pushing, you may have to add your public key:

$ heroku keys:add ~/.ssh/id_rsa.pub