Question Regarding templates in hugo

Hello, I am very new to Hugo and exploring Hugo making a custom theme. I have some doubt…
How can I navigate to the custom HTML file?
Let’s say I have about.html in layouts folder and I want to navigate to about page from header.

2nd doubt
If I create a new file in a content folder, then it will display in list page. How can I prevent showing file like, file.

Thanks for Help

Sorry, beginner questions. Read the manuals

more here