You can upload your css file to your web hosting account, and then link your website to the css by adding one line of code to your website. We can provide instructions for this if needed. Another way which we recommend and use when customizing websites, is to copy/paste any custom css coding you want to the Extras sections in the built-in Styles Manager.
You can upload your html codes that you want to integrate, and then add some coding to link to it. We can provide instructions for this if needed. But again, we would recommend copy/pasting your html coding into the Content Editor box on the Add/Edit pages (click on the html button to edit html), on your website admin panel.
You can play around with the demos/demo admin panels here: https://www.ultimatewb.com/demolinks
We have an online user manual here: https://www.ultimatewb.com/user-manual-how-to-guide
And video tutorials here: https://www.ultimatewb.com/video-tutorials and https://www.ultimatewb.com/video-tutorials-directory
Hope this helps. Please feel free to askif you have any further questions.