As a general overview, to use Web Export you do the following steps.
Install the plugin in Adobe XD
Open your project and select an artboard
Go to Web Export > Export Artboard and click Export
These steps create the web pages. You can view HTML pages on your computer with your browser.
Follow this guide step by step (the buttons along the bottom of the page navigate you along).
There is a lot to cover but you don't have to remember it all now. Get the big picture and then come to the guide to dive into the details.