You will need to either have it read from a file or from a database so figure out which works for you and learn the functions that go with the method you choose.
A template like site should have a layout that is used for each page and a place to insert the main content as well as a nav menu and any other options you choose.
This is not an easy process as you will need someway to transfer the content into the database or file...usually a web based application. I am currently working on a web based site management system and it has turned out to be quite the undertaking. It can be done but it is alot of work and a lot to learn.
My site BlackPearlWeb.com uses my application if you want to see a fairly simple setup of what you are looking for.