Sorry that you paid for a calculator in the first place.
The .html file will probably end up as a DIV tag with an ID that is added as Body code to a shape (rectangle) Placeholder.
The .css and .js would go into the Page Head code. These would require wrapping tags of <style>...</style> for the CSS and <script>...</script> for the JavaScript.
Look at Egg's example in this: https://www.talkgraphics.com/showthr...55-calculator; it's not what it done but where things go.
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