1. First of all, start with configuring the system on your computer or Mac. You can find a short tutorial about it on the GitHub website.
  2. Making a GIT repository is simple: start with the initialising of the Git repository with the following command: git init
  3. That’s it, your Git is configured, now you can create and add files in this repository (directory). When that’s done you can add those files to your first commit with this command: git add .
  4. The files are now added so it’s time for your first commit: git commit -m 'My first commit!'
  5. The final step is to push your commit remotely (can be on GitHub, BitBucket, …): git push

The final step depends on the location of your repository. Please visit the help specific for GitHub or BitBucket. Your files will now be saved online and can be shared with the world!

You can find a lot more of interesting articles and how-to’s about it. I suggest a post on StackOverflow that gives some nice links. Git Immersion is a nice tutorial for learning Git (from basic to advanced stuff). You can also find an interesting article on WebdesignersDepot with introduction specifically for web designers.