Hello,
Thank you for your question. Our guide on managing files includes sections on "how to create files," if you are not familiar with the process.
If you don't know where to create the file, please see our guide that explains what directory to put your files in?
If you just want to code a site in HTML, I recommend our Introduction to Web Design Basics tutorial.
Since your question is very general, if you are using a CMS such as Wordpress, Joomla, or Drupal, please reply and let me know, so I can provide a more specific answer.
If you have any further questions, feel free to post them below.
Thank you,
-John-Paul