Try to read as much of the User Handbook as possible to get acquainted with CMSMS.
CMSMS allows you to build a site without having to re-invent the wheel.
The Template renders all the HTML, JavaScript, CSS and content stuff, according to specific settings you can modify by changing the templates, the CSS attached to those templates, etc.
The contents can be set page by page on the Pages area OR or by using more specialized modules, such as News, Blogs, Catalogs, etc.
HTH.
