The "//" double slash represents a comment about the code from me. When I talk about code in this app I will use "{}" instead of "<>". Please keep this in mind and replace it in your own code.
Every document needs to start with the {html} tag. This lets the browser know how to load the document. Following that you will need to add the {head} tag. This is a great spot to put all your CSS and JS code, or reference locations. (You'll learn more later). Make sure to close head {/head}.
Following that you have the {body} tag. This is where all of your content goes.
To finish your document make sure you close all open tags.
When your ready to save, make sure you save at as "filename.html". It won't load as a webpage unless you use ".html".