Custom Html & Css Page

Hello,
Im a designer and you can view my wordpress site at https://www.kamclark.com. I have a theme installed for the site and its great. The problem I’m having is on my site I want to be able to show live previews of my site designs. So what I want to do is create a ‘preview’ button and when its clicked it opens to a page that shows the live preview of the site so users can view the design and view the functions. I have the html and css for the live sites but i don’t know where to place it. I tried putting the in the raw html plugin but then I still don’t have the css. I’ve tried custom page css plugins but they don’t work. Im new to wordpress and I didnt want to touch any of the .php files because I don’t want the whole theme to change I just want separate pages with the html and css. I had my developer make the html and css codes in dreamweaver and my wordpress is a hosted by goddaddy. Can someone please help me with a simple solution so I can get these live previews up and running. Thanks !