Understand it in seven pictures
What you were given, why your login is yours, why your website is yours, and the two ways to get a padlock. Start here, and it sends you to whichever of the next two is yours.
It behaves like a small computer of its own — you SSH in as root, install what you like, and put a website on it. Start with the quick start; it goes from the code somebody sent you to a padlock in the address bar.