How do I create 1 HTML file for the export

How do I turn the ZIP Export into an HTML file? I see that the index can be used to run the game from the export folder but what I am trying to do is create just 1 HTML file that contains all of the information needed to run the game.

You'll need whole zip to upload it as playable game. For example, here you can just drop your zip and test it app.netlify.com/drop

You can build to Playable Ad in Construct 3 export option.

Note: you must use Construct 3 Runtime to see it.

I am trying to do is create just 1 HTML file that contains all of the information needed to run the game.

The key question is "why do you want to do that?" - normally games run more efficiently as a series of files. The Playable Ad exporter can do a single-file export, but it is inefficient compared to a normal HTML5 export, so you should only use it if you have to.