Playtime tracking is on by default. Just play: RoRetro counts any game while your browser with RoRetro is open on your computer.

At the top of the popup you'll see:

• Today, Last 7 days and All time,
• a little bar chart of the last week,
• your games, longest first, and Recent sessions.

Playing on a phone or console with your computer's browser closed isn't counted. A browser extension can't see that.

To switch tracking off, untick Track playtime in the popup.