Opt-in feature on the landing page

Have you searched through the plugins repository for a subscription or registration plugin? That might be easier than rolling your own.

If you prefer rolling your own anyway, I would approach this by creating a custom page template to handle subscriptions. Create a page based on the template and make that a static home page in Settings.

Is this to subscribe to mailchimp news letters or something else?

I believe mailchimp offers an API where your code can add subscribers. If something else, what your code does with the subscriber information depends on exactly what that something is.

Hi ?? Its about subscribing to ConverKit…

Now, creating the popup is not a big deal (ConvertKit has several options), the issues is how to create a button in the wordpress and then make this button working that it opens the popup ??

I’m not familiar with ConverKit. How would the popup be triggered on a static HTML page? Do they provide some sample code for this? I’m guessing it’s some sort of javascript. Javascript can be triggered by adding an onclick attribute to an HTML element.

Since you want this on a landing page, you still should implement this as a static front page. The page can likely be based on the default template, the needed code simply inserted in page content. Use the text tab of the editor to do this. If that doesn’t work for some reason, create a custom page template containing the code. Base your landing page on this custom template.