Reconnecting web pages to Cascading Style Sheet Template.

10 years ago a friend with the necessary skills set up a cascading style sheet to enable me to have the html files I had made previously to look fantastic. I’ve never been able to work CSS, and in dabbling managed to separate the template files from the text files. I would like someone to reconnect them for me, and to create a template so I can create new web page content onto pages that look like the homepage. I’m sure that things will have advanced in the last 10 years, so I am open to advice on more modern approaches to putting content up at my web page.