All changes you make on the site get submitted directly to our GitHub repo, and then published through the same automated deployment process as changes made by anyone else. That way, anyone can contribute easily: whether developer or end user.
To log in, we redirect you to GitHub's site, and once you're signed in, they'll send you back here. We never see your credentials, and only get the minimum set of permissions necessary to submit changes to the Crafting Guide repo on your behalf.
GitHub offers free accounts, so even if you don't already have one, you've got nothing to lose!