I am having problems, how to get the ‘Replit Secrets’ up when using html, js, and css?
HTML/JS/CSS is the only “special” kind of Repl. Things that apply for “all” Repls do not apply, and things that apply for it do not apply to others. Like the HTML/JS/CSS Repls are not actually hosted in the Repl, and they also do not have access to secrets or Replit DB. This is because they are frontend, and if they had access to secrets or DB, anyone who used your website could view / modify them!
If you want to use these features, I recommend a backend like Python Flask or NodeJS Express, which will let you safely use these features.