Hint: he's talking about a favicon

what do I need to tilte and icon to needs to be to show up in the address bar and what size that is?

Favicons

Favicons are the little icon next to the address bar at the top of your browser.

This is more of a note to myself so I can find it later, but it might come in handy down the road to someone else:

<link rel="shortcut icon" type="image/x-icon" href="/images/favicon.ico">