It should all be straightforward. That's one of the great things about TMS WEB Core. You're up and running in a pure HTML/JS environment in a few minutes, using decades of Delphi to back you up. It's really quite fantastic in the grand scheme of things, given that HTML and JS were barely a thing when Delphi first came out of course.
So. Back to your problem. Let's have a look at your project source. If you right-click on the "WebC_UI_0.web" link in the project pane on the right, and select View Source (waaay down the list), have a look at what that is doing. Maybe it is loading up WC_UI.pas first instead of your updated WebC_UI form?