I ripped my current code from W3Schools just as a test. However, my question specifically is how can I make something like what is shown in the picture below as a login.
It has a required username and password (which I obviously won't give out for obvious reasons). I'm trying to create something like it.
You cannot do that with an html repl
You need a server side like php, node.js, falsk, ...
You need to learn how to create a webserver and do auth with it