This requires some amount of code.
That site appears to use a server-side counter; this means that each time the button is pressed, a request is made to a server running code that updates the count. There are many ways in which this could be handled, and some is dependent on what services your web host offer. A general/simple flow would be:
- On Scene Load, this is set to the inner HTML of an element to display the count
- On Button Click, an AJAX request is made to the server to increment the count.
- The server returns a new count as a result of the request in step 3
- The Inner HTML of the display element is set to this result
Create a Text element, Set the value to 0, and give it a Unique Element ID in the Identity inspector like "myCounter"
window.clickCount = 0;
window.clickCount += 1;
hypeDocument.getElementById("myCounter").innerHTML = "" + window.clickCount;
There's of course fancier ways to do this, but that's the general flow.