How do I connect dataset to html <iframe>?

See HtmlComponent,
Pass message to HtmlComponent,
See HtmlComponent run,
Run HtmlComponent, run.

You need to pass the values to the code in the HtmlComponent using messages. See the article Working with the HTML Component in Wix Code for details.

For a working example complete with messaging, see the Example: Multiple Markers Google Maps .

Good luck,

Yisrael