This page contains your entire project, including the BASIC program (even though you can't see it).
Simply save this page from your Browser. The details are different for different browsers, but it will be similar to right clicking and select "Save as..."
To stop the browser from wrapping lines, select to save as "Web page only" or "HTML only".
This is an HTML document, so when you save the page, make sure you give it an .html or .htm file extension.
Later you can open this project simply by opening the saved file in your browser. You will be automatically redirected to the www.quitebasic.com site (if not, to go to Quite BASIC).
You can also publish this page on the web. All you need to do is upload this page to your site and make a link to it.