Don't need for API Key nor Javascript. Just go to GMaps (https://www.google.com/maps?authuser=0) and:

• Find yout location from the search. If not found, click on the map where you think it is, so that a market appears.
• Right click on the marker and select "Share this location" from the popup menu.
• Select "Embed a map" tab.
• Click on "COPY HTML" or copy yourself the HTML shown with the iframe code.
• Paste the iframe code in your HTML.

This shows a map with a marker and an opened popup, at least at the time this post were published.