Welcome to the forum group.

The YouTube demos are often built around templates for demonstration purposes, as is the sample Xara gives you in the program. If your completely new with the program start drawing some shapes and importing your photos. Arrange them the way you wish. Add a text block and see how it functions. Bring in a nav bar for the top. That’s the beauty of the program.
From file under new, select the size of web page you want.

I did a quick search of videos *xara* and found many. Do you have the pro+ program, or web designer?

How about trying this one with the intro of tools. https://youtu.be/cOPJTCwP2Rg