Add my own html file used in Sydney theme

I have a html file and uploaded it into my Syndey folder on the website.
I edited the menu a new option.
I want when I click the new option on the menu and the html showed up under still in my Sydney website.
But actually, when i click the new option, it went out my Sydney website and show my html file.

This attached picture shows you what I am saying.
Please advise how to do to achive my goal.

Best regards,

Max Lee

Hi Max,

Thank you for contacting us about our theme Sydney. I am happy to help with your queries.

Can you let me know what you would like to do by adding extra HTML file to the theme?

Do you aware that all files in the main theme’s folder will be wiped out as they are replaced with new files when updating?

The secure of doing so is using a child theme instead.

aThemes Support